Send mail error 550 user unknown

send mail error 550 user unknown

It means there is no Reverse DNS record for the mail server's IP address or there is a mismatch of records in the domain used to send the email. www.hostpapa.com › Article. In 80% of cases “550 #5.1.0 address rejected” error is caused by sending mail to the wrong address. Pretty typical mistake, that can cause such errors. Emails.

Remarkable: Send mail error 550 user unknown

ERROR UNABLE TO DETERMINE THE FILE SYSTEM
Samsung printer error #04-002
Send mail error 550 user unknown
Activex runtime error 429 windows 7

Send mail error 550 user unknown - consider

One common error you can get when sending email is the “550 No Such User here” error. This error occurs when the sending email is rejected because the username cannot be found or is not accessible by the server. There are several reasons why you would get a “550 No Such User Here” error.

  • Mail file permissions are not readable or are incorrect.
  • The email address was typed incorrectly.
  • MX records are incorrect ( pointing to the wrong server ).
  • Email does not route correctly ( Remote / Local domains ).

This error can go both ways, meaning, people sending to your server may get the error and when you send from your server to another you may get the error. Depending on where the error bounce is generated from will determine what you can do about fixing the error.

If you get “550 No Such User Herebounces sending from your server to another server, you most likely will need to contact the host or email administrator of the server you are emailing to fix it.

If you are getting complaints that people sending to your server are getting this bounce, you can check / change the settings on your servers end. Below are the reasons why the 550 error may occur when you email.

Mail file permissions are not readable or are incorrect

All our servers store email in the “mail” directory of the “home” folder of your cPanel account. If the file permissions are corrupted ( sometimes caused by server moves, back up restorations, or recently uploaded files through FTP, etc.) you will get this error for all your emails. This is a simple fix. You can contact tech support to have the file permissions fixed on your server. On VPS and Dedicated servers, you can run the following from command line:

[[email protected]#### ~]$ fixperms userna5

This will reset all your file and folder permissions to folders 755 and files 644 for teh cPanle user userna5. If the email bounce is coming to you when you send to another server and it’s permissions related, the person you are emailing will need to contact their hosting provider to fix the permissions on their end.

The email address was typed incorrectly

550 No Such User Here” Errors can occur when the email address you are sending to is typed incorrectly. In this case, just make sure you have the email address spelled correctly.

MX records are incorrect ( pointing to the wrong server )

If you recently moved your domain to InMotion Hosting and you started receiving these errors, you may have a DNS nameserver or MX record problem. The MX records point your email address to a specific server. If the MX record is pointing your domain to the old hosting company and you removed all your email accounts off that server, when you go to send your email, you will get the “550 No Such User Here” error. You will want to check the following through command line:

[[email protected]#### ~]$$ dig example.com mx ; <<>> DiG 9.8.2rc1-RedHat-9.8.2-0.10.rc1.el6_3.6 <<>> example.com mx ;; global options: +cmd ;; Got answer: ;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 8149 ;; flags: qr rd ra; QUERY: 1, ANSWER: 1, AUTHORITY: 2, ADDITIONAL: 3 ;; QUESTION SECTION: ;example.com. IN MX ;; ANSWER SECTION: example.com. 14400 IN MX 0 example.com. ;; AUTHORITY SECTION: example.com. 54747 IN NS ns2.inmotionhosting.com. example.com. 54747 IN NS ns1.inmotionhosting.com. ;; ADDITIONAL SECTION: example.com. 13322 IN A 66.117.4.177 ns1.inmotionhosting.com. 11994 IN A 74.124.210.242 ns2.inmotionhosting.com. 11994 IN A 70.39.150.2

The example above shows that domain example.com points to the ns1.inmotionhosting.com and ns2.inmotionhosting.com nameservers and that the MX routes to the InMotion Hosting server.

Make sure your nameservers are pointing to us. If your nameservers do not point to our server, then your domain will not route to our server unless you make special DNS changes at the host the nameservers point to.

Make sure the MX records for your domain are sending to the correct server. If your domain does point to the correct server, check the MX records to see if the email is pointing to the correct server in the cPanel MX entry.

If your nameservers and DNS are correct, then you will need to check the email routing. If the bounce message is from you sending to another server, then the person receiving the email will need to check with their email provider for a resolution.

Email does not route correctly ( Remote / Local domains )

In the case that you are receiving bounces to a specific email address, you will need to find the MX records and the nameservers for the receiving domains DNS. Run the following DIG in the Linux command line to find the Receiving servers nameservers.

To find out if your domain is on the receiving email servers DNS nameserver, you can DIG the domain for their nameservers. Once you get the nameservers for the receiving domain, you can check the DNS for your domain using their nameservers. Below will explain in detail.

Dig the receiving server domain to find the nameservers:

Below shows what a DNS MX record DIG looks like for notexample.com.

[[email protected]#### ~]$ dig notexample.com mx ; <<>> DIG 9.8.2rc1-RedHat-9.8.2-0.10.rc1.el6_3.6 <<>> notexample.com ;; global options: +cmd ;; Got answer: ;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 8587 ;; flags: qr rd ra; QUERY: 1, ANSWER: 1, AUTHORITY: 2, ADDITIONAL: 2 ;; QUESTION SECTION: ;notexample.com. IN A ;; ANSWER SECTION: notexample.com. 14400 IN MX 0 notexample.com. ;; AUTHORITY SECTION: notexample.com. 85619 IN NS ns1.somenameserver.com.notexample.com. 85619 IN NS ns2.somenameserver.com. ;; ADDITIONAL SECTION: notexample.com. 13322 IN A 25.22.80.62 ns2.somenameserver.com. 18391 IN A 25.22.80.62 ns1.somenameserver.com. 18391 IN A 25.22.67.43 ;; Query time: 1 msec ;; SERVER: 74.124.198.200#53(74.124.198.200) ;; WHEN: Thu Mar 7 06:08:06 2013 ;; MSG SIZE rcvd: 136

The results of this DIG shows that the nameservers for the receiving server notexample.com has the nameservers of ns1.somenameserver.com and ns2.somenameserver.com. The MX record points to notexample.com which has an IP that points to the server the nameservers are on. Next you can check your domain in the receiving server nameservers.

Checking if your domain is in another servers DNS:

Now that you have the receiving server nameservers for the notexample.com domain, you can DIG the DNS records at the receiving servers end to see if your domain is in their DNS nameserver. The following is an example of the DIG command in shell that will look up example.com on the notexample.com server.

dig @ns1.somenameserver.org example.com ; <<>> DiG 9.8.2rc1-RedHat-9.8.2-0.10.rc1.el6_3.6 <<>> @ns1.somenameserver.org example.com ; (1 server found) ;; global options: +cmd ;; Got answer: ;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 11023 ;; flags: qr aa rd; QUERY: 1, ANSWER: 1, AUTHORITY: 2, ADDITIONAL: 2 ;; WARNING: recursion requested but not available ;; QUESTION SECTION: ;example.com. IN A ;; ANSWER SECTION: example.com. 14400 IN A 70.39.251.58 ;; AUTHORITY SECTION: example.com. 86400 IN NS ns2.somenameserver.org.example.com. 86400 IN NS ns1.somenameserver.org. ;; ADDITIONAL SECTION: ns1.somenameserver.org. 14400 IN A 70.39.251.58 ns2.somenameserver.org. 14400 IN A 70.39.251.58 ;; Query time: 66 msec ;; SERVER: 70.39.251.58#53(70.39.251.58) ;; WHEN: Fri Mar 8 06:16:18 2013 ;; MSG SIZE rcvd: 140

The previous response shows that example.com is in the DNS on the notexample.com server. This means that the emails sent to notexample.com are seeing example.com in their DNS, looking for the email address on the notexample.com server, and rejecting it because there is no email address on the server.

To fix this, you will need to contact the hosting company or the domain owner that you are sending to, telling them that your emails cannot go through to their server because your domain is in their DNS. They will ned to “Kill the DNS, change the routing to remote on the receiving server, or remove your domain from their DNS nameserver.

If your domain is not in their DNS nameserver:

If example.com was NOT found in the nameserver on the receiving server you will get the following not found response.

dig @ns1.inmotionhosting.com google.com ; <<>> DiG 9.8.2rc1-RedHat-9.8.2-0.10.rc1.el6_3.6 <<>> @ns1.inmotionhosting.com google.com ; (1 server found) ;; global options: +cmd ;; Got answer: ;; ->>HEADER<<- opcode: QUERY, status: SERVFAIL, id: 63529 ;; flags: qr rd ra; QUERY: 1, ANSWER: 0, AUTHORITY: 0, ADDITIONAL: 0 ;; QUESTION SECTION: ;google.com. IN A ;; Query time: 0 msec ;; SERVER: 74.124.210.242#53(74.124.210.242) ;; WHEN: Fri Mar 8 06:20:03 2013 ;; MSG SIZE rcvd: 28

In this case, you can try checking your email routing. If you are sending from your server with us, you will need to set the email routing to local in your MX entry of your cPanel. If you are using a 3rd party application like Google APPs, you will need the routing set to remote.

If this does not fix the problem, then you will want to contact tech support to find out if there is a routing issue with your DNS.

How to fix "550 5.1.1 User unknown" Error when Sending to a Distribution Group

You may find that after you create a new distribution group in Exchange 2010, you cannot send SMTP email to it from the Internet or internal relay hosts.  When you do, you receive a "550 5.1.1 User unknown" error .  If you send email to the distribution group internally using Outlook or OWA, it works just fine.

This happens because Exchange 2010 automatically sets the attribute Require that all senders are authenticated to enabled by default. 

To clear this setting, view the properties of the distribution group and double-click Message Delivery Restrictionson the Mail Flow Settingstab:

Then clear the checkbox for Require that all senders are authenticated and click OK.


At first I thought this might be due to the fact that my client is using Edge Transport servers and that the Block messages sent to recipients that do not exist in the directory setting was enabled.  This is shown below from the Edge server's Recipient Filtering properties:

I tested this by running the following cmdlet:

Test-EdgeSynchronization -VerifyRecipient zzz.domain.com

Sure enough, the result shows, NotSynchronized - Recipient doesn't exist in source Active Directory, as shown below:


Somewhat surprisingly, this result does not change when Require that all senders are authenticatedis disabled.

I can't believe I've never run into this until now. 

Before you ask, there is no way to change the default behavior of Exchange 2010 to create all distribution groups with the authentication setting set to disabled (unchecked).

Resolving Error Messages


Cause:

When reads from any source that might time out, such as an SMTP connection, the program sets a timer to the value of various options before reading begins. If the read is not completed before the timer expires, this message appears and reading stops. Usually, this situation occurs during . The mail message is then queued for later delivery.

Solution:

If you see this message often, increase the value of various options in the file. If the timer is already set to a large number, look for hardware problems, such as poor network cabling or connections.


Cause:

This message indicates that the destination host machine, which is specified by the portion of the address after the at sign (@), was not found during domain name system (DNS) lookup.

Solution:

Use the command to verify that the destination host exists in that domain or other domains, perhaps with a slightly different spelling. Otherwise, contact the intended recipient and ask for a proper address.


Cause:

This message indicates that the intended recipient, who is specified by the portion of the address before the at sign (@), could not be located on the destination host machine.

Solution:

Check the email address and try again, perhaps with a slightly different spelling. If this remedy does not work, contact the intended recipient and ask for a proper address.


Cause:

This message usually indicates that the local host is trying to send mail to itself.

Solution:

Check the value of the macro in the file to ensure that this value is a fully qualified domain name.

Description:

When the sending system provides its host name to the receiving system in the SMTP command, the receiving system compares its name to the sender's name. If these names are the same, the receiving system issues this error message and closes the connection. The name that is provided in the command is the value of the macro.

For additional information, refer to .


Cause:

This error message occurs if you set up an MX record and make host the mail exchanger for domain . However, you fail to configure host to know that it is the mail exchanger for domain .

Also, another possibility is that both the sending system and the receiving system are identifying as the same domain.

Solution:

For instructions, refer to .


Description:

This is an old message, which replaced and is now replaced by the message.

Solution:

Follow the instructions that were provided for resolving this error message, .


Cause:

When you try to send mail to a user, the error is displayed. The user is on the same system.

Solution:

Check for a typographical error in the entered email address. Otherwise, the user could be aliased to a nonexistent email address in or in the user's file. Also, check for uppercase characters in the user name. Preferably, email addresses should not be case sensitive.

For additional information, refer to .

550 Blocked error explained

550 Blocked error or 550 Requested action not taken: mailbox unavailable is an SMTP (Simple Mail Transfer Protocol) error code. Put simply, this message means that the email you sent was blocked by the recipient's email hosting server, and returned to you.

Note: This error is often a problem at the recipient’s end, meaning it is probably not caused by your own email hosting server.

SMTP (Simple Mail Transfer Protocol) is a set of standardised rules on sending and receiving emails (electronic mails). Most often, it is used along with POP3 (Post Office Protocol 3) or IMAP (Internet Message Access Protocol) because it has limitations with regards to queueing and receiving messages. Hence, the usual setup for emails is to use SMTP for outgoing emails while it is POP3 or IMAP for incoming emails.

This SMTP 550 error code can be written in several different ways. Usually, the phrasing of the error message depends on the hosting server sending the error. Here are some common ways they may be phrased:

  • SMTP Error 550
  • SMTP Error 5.5.0
  • 550 Invalid recipient
  • 550 User account is unavailable
  • 550 – Requested actions not taken as the mailbox is unavailable.
  • 550 Address rejected
  • 550 No such user here
  • 550 Not our Customer
  • 550 Account not available
  • Remote host said: 550 – [email protected], this MYDOMAIN.COM
    Mailbox Does Not Exist – Giving up

  • 240.240.240.240 does not like recipient
    Remote host said: 550-Verification failed for u[email protected]
    550-Previous (cached) callout verification failure
    550 Sender verify failed Giving up on 240.240.240.240.

  • The attached file had the following undeliverable recipient(s): [email protected]

    Transcript of session follows:
    Command: Data...
    Response: 550 Cyberoam Anti Spam Engine has identified this email as a spam. Refid:str=0001.0A0B0206.4BA7422C.01F5,ss=1,vtr=str,vl=0,pt =

  • 550-Verification failed for [email protected] - 550-Unrouteable address - 550 Sender verify failed (in reply to RCPT TO command)
Note:If there is a system-wide problem with the recipient's hosting server or the host is temporarily down, the following error message is also possible:

  • 5.1.0 - Unknown address error 550-'Mailbox is inactive'

What are the causes of a 550 Blocked error?

The 550 SMTP error is one of the most common error codes you may encounter. For this particular error code, here are some of the possible causes:

  1. Your IP address is blocked by the recipient’s email hosting server.
  2. Your email address has been compromised and has been blocked by recipient’s hosting server.
  3. You are sending an email using an ISP that is different to the one you are currently logged on to.
  4. The recipient’s email address cannot be found, or does not exist.
  5. The recipient’s email has been suspended or temporarily disabled.
  6. Your own domain name is invalid, cannot be found, or has been blocked.
  7. Your email message is being treated as spoofed, and has been rejected by the recipient’s email hosting server.
  8. The recipient’s email hosting server tried to verify the sender email address, but was unable.
  9. The recipient’s hosting server is down, and is unable to receive the email.
  10. The recipient’s inbox is full, and is unable to receive the email.
  11. The recipient’s email hosting has an anti-spam firewall, and has labelled your message as spam.
  12. Your own Internet gateway has a firewall, or filtering feature, that intercepted your own email, regarded it as spam, and blocked it to stop you from accidentally sending out spam or a virus-infected email.
  13. Your email account has been hacked, has been used to send out tons of spam mail, and so has been blocked by the recipient’s SPF (Sender Policy Framework).

SMTP 550 Error is often a problem at the recipient’s end, which means this error is usually caused by factors outside your email hosting server.

Easy Ways to Troubleshoot a 550 Blocked error

Although the SMTP 550 Error is usually an error on the recipient’s end, there may still be ways you can fix the problem. Here are some possible solutions:

  1. Double-check the recipient’s email address. Make sure you have the right email address and there are no misspellings, typos, or extra spaces on it.

  2. Confirm with the recipient that you have their correct email address. If you have checked the email address and you are certain you typed it correctly, but you still get an SMTP 550 Error, then perhaps you got the wrong email address from the recipient. It could also be that they have changed the domain name or any other part of the address.

  3. Check your own email address and message. Make sure that your sender email is typed correctly, and check that your email has content. Some email hosting servers can reject emails that are blank, or have no content.

  4. Try changing your outgoing mail port to 26 or 465. Some servers block port 25 because spammers often use it to send spam, or spoofed emails.

  5. Scan your computer for viruses and malware. Technically, email addresses don’t get infected; it’s the computers or the hard drives that do. Install a reliable antivirus program, and scan your computer. After the scan, change your email password, just in case you have been hacked.

  6. Re-try sending the email after a few minutes, or hours. It is possible that the recipient’s server is just temporarily down and may come back up after a while. If you get the error message again, even after a few hours, contact the recipient and inform them that their hosting may be down.

  7. Use your ISP’s outgoing mail server. Sometimes, it is your own Internet Service Provider or Internet gateway filtering and blocking your emails. If this is the case, you can try using your ISP’s outgoing mail server. You can check our partial list of outgoing mail servers for some popular ISPs here .

  8. Contact your ISP. A good solution may be to ask your Internet Service Provider for assistance. After all, they are the one who know their system best, and may be able to help.

  9. Change all your passwords. Be sure to use a random mix of letters, numbers, and special characters to make a really strong password. Also change your recovery options, since if hackers have gained access to your account they would probably aware of these options, too. As added protection, make a habit of changing your passwords regularly.

Was this helpful?YesNo58% of people found this helpful.

Fantastic...Thank you for your feedback =)

Sorry... Please submit a support ticket or try another search.

‘550 5.1.1 User unknown’ is one of the common issues reported by users sending mails to Exchange servers. 550 error means there is some problem with the recipient server which makes it unable to deliver the mail.

In our role as Website Support specialists for web hosting companies, we’ve seen senders sending mails from other servers such as Exim, Postfix, etc. to Exchange servers, seeing this error in the bounce message:

550 5.1.1 User unknown (in reply to RCPT TO command)

See how we can support your websites!

Today we’ll see the major causes of this email error and how to fix them.

1. Wrong recipient address

Sender would get the bounce message ‘550 5.1.1 User unknown‘, if the recipient mail server is unable to find the recipient mail account in it.

At times, a typo in the email address of the recipient can cause this email delivery failure. A missing alphabet or an incorrect character can end up messing an email address.

It is possible that an email address that once existed, gets deleted or moved from the recipient mail server. In such cases, the recipient server would be unable to deliver the mail.

Even a misconfiguration or bug in the recipient mail server can cause the email account to get disabled and mails to that account to fail.

If the recipient doesn’t have the email address that you’re sending to, it will bounce the mail with the error message ‘550 5.1.1 User unknown‘.

Solution:

Always validate the recipient email address you’ve given in the email for any spelling mistakes or errors. If everything is fine at your end, confirm whether the email account actually exists.

[ Are your websites helping you get business? Our website support team gives you custom website solutions and fix all errors in your website in no time. ]

2. Incorrect DNS settings for the domain

Email Error 550 can also occur when the DNS settings for the recipient domain are not correct or the MX entry is not resolving correctly.

For instance, the MX records for the domain could be wrongly resolving to the recipient mail server instead of its intended server.

In such cases, recipient mail server cannot find the account and will bounce the mail. DNS issues can also occur due to any wild card DNS or SPF entry that is not set correctly.

These DNS related errors or wrongly mail server MX settings can end up giving an error message ‘550 5.1.1 User unknown‘ to the sender.

Solution:

Verify the MX records for a domain, using the command:

dig domain.com MX

If you notice DNS errors or missing MX records, then contact the recipient server support and get it fixed.

3. Email filters set for the domain

Some recipient mail accounts can have email filters or forwarders set. A catchall address or forwarder that relay to a non-existing account, can end up causing 550 errors.

Filtering for incoming mails using email filters or anti-spam firewalls, can end up bouncing emails from certain sender servers, returning a 550 error message.

Though 550 errors are usually related to recipient mail server issues, at times some filtering or firewalls applied on outgoing mails in the sender server can also cause this error.

For instance, some programs such as Google Apps modify the ‘To address’ of outgoing mails. Updating the recipient address to a non-existing address, can show error ‘550 5.1.1 User unknown‘.

Solution:

Check your outgoing firewalls and rules, if any. If all good, contact recipient server support and get the email filters verified for any erroneous filters or rules that can be blocking mails.

[ A single misconfiguration may break your site! Click here for a customized and error-free website to help you boost your business. ]

4. Mail server configuration errors

Apart from the above reasons, some configuration mistakes in the mail server can also end up causing the error 550 for domains in it.

A server-wide custom filter that blocks mail from certain senders, a default forwarder that relay mails to another address, custom email software or security restrictions, all can lead to email errors.

Sometimes, the issue may be a temporary one. In those cases, the sender mail server will re-attempt the delivery of failed emails, based on its configuration.

Solution:

Examining the error logs and email headers of the bounced mail would help identify the issue with the mail server. Testing email routing in the server would also help detect any issues.

Disabling unwanted filters and rules and ruling out any restrictions that cause the emails to bounce, is crucial in fixing the issue.

One common error you can get when sending email is the “550 No Such User here” error. This error occurs when the sending email is rejected because the username cannot be found or is not accessible by the server. There are several reasons why you would get a “550 No Such User Here” error.

  • Mail file permissions are not readable or are incorrect.
  • The email address was typed incorrectly.
  • MX records are incorrect ( pointing to the wrong server ).
  • Email does not route correctly ( Remote / Local domains ).

This error can go both ways, meaning, people sending to your server may get the error and when you send from your server to another you may get the error. Depending on where the error bounce is generated from will determine what you can do about fixing the error.

If you get “550 No Such User Herebounces sending from your server to another server, you most likely will need to contact the host or email administrator of the server you are emailing to fix it.

If you are getting complaints that people sending to your server are getting this bounce, you can check / change the settings on your servers end. Below are the reasons why the 550 error may occur when you email.

Mail file permissions are not readable or are incorrect

All our servers store email in the “mail” directory of the error creating cursor handle t-sql folder of your cPanel account. If the file permissions are corrupted ( sometimes caused by server moves, back up restorations, or recently uploaded files through FTP, etc.) you will get this error for all your emails. This is a simple fix. You can contact tech support to have the file permissions fixed on your server. On VPS and Dedicated servers, you can run the following from command line:

[[email protected]#### ~]$ fixperms userna5

This will reset all your file and folder permissions to folders 755 and files 644 for teh cPanle user userna5. If the email bounce is coming to you when you send to another server and it’s permissions related, the person you are emailing will need to contact their hosting provider to fix the permissions on their end.

The email address was typed incorrectly

550 No Such User Here” Errors can occur when the email address you are sending to is typed incorrectly. In this case, just make sure you have the email address spelled correctly.

MX records are incorrect ( pointing to the wrong server )

If you recently moved your domain to InMotion Hosting and you started receiving these errors, you may have a DNS nameserver or MX record problem. The MX records point your email address to a specific server. If the MX record is pointing your domain to the old hosting company and you removed all your email accounts off that server, when you go to send your email, you will get the “550 No Such User Here” error. You will want to check the following through command line:

[[email protected]#### ~]$$ dig example.com mx ; <<>> DiG 9.8.2rc1-RedHat-9.8.2-0.10.rc1.el6_3.6 <<>> example.com mx ;; global options: +cmd ;; Got answer: ;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 8149 ;; flags: qr rd ra; QUERY: 1, ANSWER: 1, AUTHORITY: 2, ADDITIONAL: 3 ;; QUESTION SECTION: ;example.com. IN MX ;; ANSWER SECTION: example.com. 14400 IN MX 0 example.com. ;; AUTHORITY SECTION: example.com. 54747 IN NS ns2.inmotionhosting.com. example.com. 54747 IN NS ns1.inmotionhosting.com. ;; ADDITIONAL SECTION: example.com. delphi shfileoperation error 13322 IN A 66.117.4.177 ns1.inmotionhosting.com. 11994 IN A 74.124.210.242 ns2.inmotionhosting.com. 11994 IN A 70.39.150.2

The example above shows that domain example.com points to the ns1.inmotionhosting.com and ns2.inmotionhosting.com nameservers and that the MX routes to the InMotion Hosting server.

Make sure your nameservers are pointing to us, send mail error 550 user unknown. If your nameservers do not point to our server, then your domain will not route to our server unless you make special DNS changes at the host the nameservers point to.

Make sure the MX records for your domain hard disk 301 error sending to the correct server. If your domain does point to the correct server, check the MX records to see if the email is pointing to the correct server in the cPanel MX entry.

If your nameservers and DNS are correct, then you will need to check the email routing. If the bounce message is from you sending to another server, then the person receiving the email will need to check with their email provider for a resolution.

Email does not route correctly ( Remote / Local domains )

In the case that you are receiving bounces to a specific email address, you will need to find the MX records and the nameservers for the receiving domains DNS. Run the following DIG in the Linux command line to find the Receiving servers nameservers.

To find out if your domain is on the receiving email servers DNS nameserver, you can DIG the domain for their nameservers. Once you get the nameservers for the receiving domain, you can check the DNS for your domain using their nameservers. Below will explain in detail.

Dig the receiving server domain to find the nameservers:

Below shows what a DNS MX record DIG looks like for notexample.com.

[[email protected]#### ~]$ dig notexample.com mx ; <<>> DIG 9.8.2rc1-RedHat-9.8.2-0.10.rc1.el6_3.6 <<>> notexample.com ;; global options: +cmd ;; Got answer: ;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 8587 ;; flags: qr rd ra; QUERY: 1, ANSWER: 1, AUTHORITY: 2, ADDITIONAL: 2 ;; QUESTION SECTION: ;notexample.com. IN A ;; ANSWER SECTION: notexample.com. 14400 IN MX 0 notexample.com. ;; AUTHORITY SECTION: notexample.com. 85619 IN NS ns1.somenameserver.com.notexample.com. 85619 IN NS ns2.somenameserver.com. ;; ADDITIONAL SECTION: notexample.com. 13322 IN A 25.22.80.62 ns2.somenameserver.com. 18391 IN A 25.22.80.62 ns1.somenameserver.com. 18391 IN A 25.22.67.43 ;; Query time: 1 msec ;; SERVER: 74.124.198.200#53(74.124.198.200) ;; WHEN: Thu Mar 7 06:08:06 2013 ;; MSG SIZE rcvd: 136

The results of this DIG shows that the nameservers for the receiving server notexample.com has the nameservers of ns1.somenameserver.com and ns2.somenameserver.com. The MX record points to notexample.com which has an IP that points to the server the nameservers are on. Next you can check your domain in the receiving server nameservers.

Checking if your domain is in another servers DNS:

Now that you have the receiving server nameservers for the notexample.com domain, you can DIG the DNS records at the receiving servers end to see if your domain is in their DNS nameserver. The following is an example of the DIG command in shell that will look up example.com on the notexample.com server.

dig @ns1.somenameserver.org example.com terrorist takedown war in colombia.iso <<>> DiG 9.8.2rc1-RedHat-9.8.2-0.10.rc1.el6_3.6 <<>> @ns1.somenameserver.org example.com ; (1 server found) ;; global options: +cmd ;; Got answer: ;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 11023 ;; flags: qr aa rd; QUERY: 1, ANSWER: 1, AUTHORITY: 2, ADDITIONAL: 2 ;; WARNING: recursion requested but not available ;; QUESTION SECTION: ;example.com. IN A ;; ANSWER SECTION: example.com. 14400 IN A 70.39.251.58 ;; AUTHORITY SECTION: example.com, send mail error 550 user unknown. 86400 IN NS ns2.somenameserver.org.example.com. 86400 IN NS ns1.somenameserver.org. ;; ADDITIONAL SECTION: ns1.somenameserver.org. 14400 IN A 70.39.251.58 ns2.somenameserver.org. 14400 IN A 70.39.251.58 ;; Query time: 66 msec ;; SERVER: 70.39.251.58#53(70.39.251.58) ;; WHEN: Fri Mar 8 06:16:18 2013 ;; MSG SIZE rcvd: 140

The previous response shows that example.com is in the DNS on the notexample.com server. This means that the emails sent to notexample.com are seeing example.com in their DNS, looking for the email address on the notexample.com server, and rejecting it because there is no email address on the server.

To fix this, you will need to contact the hosting company or the domain owner that you are sending to, telling them that your emails cannot go through to their server because your domain is in their DNS. They will ned to “Kill the DNS, change the routing to remote on the receiving server, or remove your domain from their DNS nameserver.

If your domain is not in their DNS nameserver:

If example.com was NOT found in the nameserver on the receiving server you will get the following not found response.

dig @ns1.inmotionhosting.com google.com ; <<>> DiG 9.8.2rc1-RedHat-9.8.2-0.10.rc1.el6_3.6 <<>> @ns1.inmotionhosting.com google.com ; (1 server found) ;; global options: +cmd ;; Got answer: ;; ->>HEADER<<- opcode: QUERY, status: SERVFAIL, id: 63529 ;; flags: qr rd ra; QUERY: 1, ANSWER: 0, AUTHORITY: 0, ADDITIONAL: 0 ;; QUESTION SECTION: ;google.com. IN A ;; Query time: 0 msec ;; SERVER: send mail error 550 user unknown ;; WHEN: Fri Mar 8 06:20:03 2013 ;; MSG SIZE rcvd: 28

In this case, you can try checking your email routing. If you are sending from your server with us, you will need to set the email routing to local in your MX entry of your cPanel. If you are using a 3rd party application like Google APPs, you will need the routing set to remote.

If this does not fix the problem, then you will want to contact tech support to find out if there is a routing issue with your DNS.

How to Solve ‘550 5.1.1 User Unknown’ Error?

The impact which the error ‘550 5.1.1 User unknown’ creates in various servers is different and the solutions too, send mail error 550 user unknown. Yet the major causes of error are:

  • Due to the usage of wrong address
  • Wrong DNS settings for the domain
  • Errors in mail server configuration
  • The filters (in the form of an email) set for the domain.

There is no universal solution for the error in all servers like Exchange, Exim, Qmail, etc. Each server needs to be audited and the report should be documented. So in this blog, we provide you information which will help you to manage the ‘550 5.1.1 User unknown’ error with better insights.

In Exchange Servers

The error ‘550 5.1.1 User unknown’ is a common issue among server administrators who handle Microsoft Exchange Servers. The main reason for the display send mail error 550 user unknown the error message is the security parameters followed by the senders. These errors can happen with a distribution group of email addresses and a single account as well. The security parameter which is implemented by Microsoft Exchange 2010 authenticates the sender to prevent spamming and it is enabled on the server by default. While sending, except local email addresses, send mail error 550 user unknown, all other get bounced with 550 errors. It is possible to manage this issue by checking whether any security restriction is associated with the emails which are causing the bounce and email error 550. In order to remove the restriction, do the following steps.

Step 1: Open the Exchange management console.

Step 2:  After expanding send mail error 550 user unknown recipient configuration, click on the mailbox or list

Step 3:  List the mail box which is having the issue

Step 4: From the properties button go to ‘Mail Flow Settings’ tab

Step 5:  Go for ‘Message Delivery Restrictions’ then click properties.

Step 6:   clear the checkbox titled ‘Require that all senders are authenticated’ and click OK.

In Exim for cPanel/ DirectAdmin and WHM servers

Most of the cPanel and DirectAdmin use Exim mail server in two ways. When some of the servers use it as default installation, others go for the customization. The error message ‘550 5.1.1 User unknown’ is not common in Exim servers. So if you are confronted with such an archos firmware download error, the route cause needs to be identified.  The recipient email address has to be checked for tracking the ‘typo errors’ and also you have to ensure that no custom email programs are messing up with mail server settings. The filters and custom rules added to the Exim mail or the specific domain need to undergo through strict verification in order to identify and fix the 550 email errors.

 

In Qmail and Postfix for Plesk servers

Two things need to be verified in order to resolve the error ‘550 5.1.1 User unknown’ in Qmail and Postfix for Plesk servers. Verify whether the recipient domain is properly resolving to the correct server or not and secondly ensure if it has its mail server configured on the server as well. If the MX points to the local servers and found it as disabled, try to enable it. Turn off the mail servers for the domain if the email service for the domain is hosted elsewhere. Make sure that there are no filters or custom rules in the Qmail or Postfix mail server which is messing up with the mail delivery. In order to achieve this conduct a detailed examination of bounced headers and mail logs will make it for you.

Conclusion

Identifying and solving the ‘550 5.1.1 User unknown’ error is difficult compared to other server issues. It is even difficult to understand the error based on the error message. There are more variants for ‘550 5.1.1 User unknown’ such as ‘550 MAILBOX NOT FOUND’, ‘550 Unrouteable address’, ‘550 mailbox temporarily disabled’, ‘550 No such user here’, etc. A detailed study in accordance with various servers helps to track the error and to formulate a solution. Since this type of errors is relative to the change in server, instead of a direct solution, this blog will direct you precisely in your study and to track the error.

Read these next.

Estimados,

Yo estoy obteniendo el siguiente rebote, es con 1 usuario en particular y solo para remitentes externos, se chequeo el antispam local y no tiene remitentes bloqueados, lo mismo que el servidor, agradeceria la ayuda.

Saludos.

De: Mail Delivery Subsystem

Fecha: Monday, October 26, 2015

Asunto: Test11

Para: [email protected]

Delivery to the following recipient failed permanently:

[email protected]

Technical details of permanent failure:

Google tried to deliver your message, but it was rejected by the server for the recipient domain mapfre.com.ar by mail.mapfre.com.ar, send mail error 550 user unknown. [200.51.204.75].

The error that the other server returned was:

550 5.1.1 Send mail error 550 user unknown address rejected: User unknown

----- Original message -----

DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed;

d=gmail.com; s=20120113;

h=from:content-type:content-transfer-encoding:mime-version:subject

:message-id:date:to;

bh=Ko86eTdCj+WOMCk+aT68Z60oID1cds9EVSHAPUf+zUM=;

b=XqKJ2qfoS2kfXITS/KxiTaXKNtwv/sRzfy89b/5saql2rkhvcpwMgzHQBXEoghvnPP

2NWbgC8zFM8m+eP8g1lM4MH6MOHNHfx0DDHl2sJLF5vn56u3QpigP52+kmXpJT4zkJQ5

VjKiXwnXA8X3S7vR0+zFomFcmB7viWBvyXp7zLySc5WfnXtf5hnR60GCoRhWOpAsYMnk

Q6uXplDy2y+DQFTeZoGyZLiV5MlH/K2hrNtENCvuViI8ouhKl8Rc2GTMZ2OfHyF7cE5r

1cAruZR71RRSuFCBClg4U/Fnbe/qHBshZ9sd3ImQ5C+zajIGYByfNpC89czQLARoh0wa

fWOw==

X-Received: by 10.140.194.5 with SMTP id p5mr42354087qha.84.1445871184936;

Mon, 26 Oct 2015 07:53:04 -0700 (PDT)

Return-Path:

Received: from [192.168.0.98] ([186.22.220.217])

by smtp.gmail.com with ESMTPSA id b60sm13176061qga.33.2015.10.26.07.53.04

for

(version=TLSv1 cipher=ECDHE-RSA-RC4-SHA bits=128/128);

Mon, 26 Oct 2015 07:53:04 -0700 (PDT)

From: [email protected]

Content-Type: text/plain;

charset=us-ascii

Content-Transfer-Encoding: 7bit

Mime-Version: 1.0 (1.0)

Subject: Test11

Message-Id: <[email protected]>

Date: Mon, 26 Oct 2015 11:53:03 -0300

To: [email protected]

X-Mailer: iPhone Mail (13A452)

As a company providing technical support for clients servers and infrastructures – we often face with situations when our customers have 550 permanent failure for one or more recipients error or any kind of another 550 error. Such errors may occur with emails in Exchange and Postfix servers.

Reasons of getting and different kinds of 550 error message

Example of messages associated with this error:

550 permanent failure for one or more recipients

550 User unknown

550 5.1.1 Sorry, no mailbox here by that name

550 Requested action not taken: mailbox unavailable

550 5.1.1 Is not a valid mailbox

550 No such user here

550 Invalid recipient

550 #5.1.0 Unknown address error ‘MAILBOX NOT FOUND’

550 5.1.1 The email account that you tried to reach does not exist

550 5.1.1 Recipient address rejected: User unknown in relay recipient table

554 delivery error: This user doesn’t have an account

554 delivery error: Sorry your message to [email] cannot be delivered. This account has been disabled or discontinued

550 #5.1.0 Address rejected

Of course, there are other similar error messages that you might see we’ve just focused on the most common ones. There are two main reasons for getting such as “550 permanent failure for one or more recipients” message – the issue may be in the sender or recipient server.
[pbutton]

Recipient server issues:

If you’ll see a message similar to any of these, you must contact the recipient by other means (telephone, Facebook or any other form of contact) asking the recipient to contact the email server’s hosting company or the network administrator of the company (in the case of corporate emails) to fix the problem. Ideally, you should forward the error message to the recipient using a working email address, so he or she can forward to the person in charge of the email server’s configuration.

Sometimes you may send an email to the wrong email.

In 80% of cases “550 #5.1.0 address rejected” error is caused by sending mail to the wrong address. Pretty typical mistake, that can cause such errors. Emails may also be bounced if you are sending an email to a non-existing address, or an address that is no longer in use on the recipient server.
If the problem is in validity of the recipient address – you will get “550 5.1.1: Recipient address rejected“.
To solve this you just need to check if an address you are sending an email is existent and typed correctly.

Misconfigured MX record on the recipient domain

The other reason for bounced email may be related to the misconfiguration of the recipient’s MX record. If the address that you are sending a message is resolving wrongly – the recipient’s server will be unable to process an email account and the email will bounce.
To solve this you should check the MX records of recipient domain by the following command:

dig recipientdomain.com MX

If you notice any misconfiguration in MX records – you should contact recipients server support with a request to solve the issue. Note that this error is on the recipient’s side, not yours!

Recipients mail server misconfiguration

The majority of the mail servers are tuned with security measures and custom security solutions. Such security configurations like firewall and spam filters are usually used to block undesirable emails from reaching the server and spam filtering.
First of all, you need to understand whether the recipient’s firewall is blocking your server or not:

telnet recipientdomain.com 25

If a firewall or spam filters are bouncing your email – verify the recipient’s filters and blacklists.
[havequestion]

Sender server issues:

Let’s now review a few error messages you can see if there is something wrong with your email server configuration or if your email server is flagged as a source of spam. The root of such as “550 #5.1.0 address rejected” errors may be caused by sender server issues.

You are sending spam

The majority of mail servers (such as Postfix and Exchange) have an option to bounce emails from non-verifiable emails. Also, most of mail servers check blacklists before pushing the mail to recipient, and if your mail server is blacklisted – your email will be bounced.
To make sure your mails are not considered crack error nuker spam – check if your SPF records exist and RDNS is configured accurately:

host your_IP_address

Also you need to make sure that your IP address is not blacklisted.

Your email account is hacked

Hackers are not sleeping nowadays, and you can’t be 100% sure that your account is secure and protected. If you notice any emails that you didn’t send, or some spam that is been sent from your account without your involvement – check the logs and ensure you don’t have any script for mass spam mailing.
First thing you need to do is check if there are any spamming scripts. If there are no such – change the password, using some kind of strong random password generator and restrict the access to your mail only for several IPs.

Sender server misconfiguration

Even such simple issues in configuration like configuration of recipient domain as a local domain in the sender server may cause email bouncing. Yeah, that’s a pretty weird, send mail error 550 user unknown, but still a reason to double-check your mail server configuration 🙂
[pbutton]

Let’s summarize when you can get ‘550 permanent failure for one or more recipients’:

There may be many reasons that cause “550 permanent failure for one or more recipients” error, that can both be related to recipient side and sender side. You need to check the valiance of recipients email and if you typed it correctly. If this will be not enough – ITsyndicate will be happy to help you.

error network down chto oznachaet Previous Article send mail error 550 user unknown Next Article

‘550 5.1.1 User unknown’ is one of the common issues reported by users sending mails to Exchange servers. 550 error means there is some problem with the recipient server which makes it unable to deliver the mail.

In our role as Website Support specialists for web hosting companies, we’ve seen senders sending mails from other servers such as Exim, Postfix, etc. to Exchange servers, seeing this error in the bounce message:

550 5.1.1 User unknown (in reply to RCPT TO command)

See how we can support your websites!

Today we’ll see the major causes of this email error and how to fix them.

1. Wrong recipient address

Sender would get the bounce message ‘550 5.1.1 User unknown‘, if the recipient mail server is unable to find the recipient mail account in it.

At times, a typo in the email address of the recipient can cause this email delivery failure. A missing alphabet or an incorrect character can end up messing an email address.

It is possible that an email address that once existed, gets deleted or moved from the recipient mail server. In such cases, the recipient server would be unable to deliver the mail.

Even a misconfiguration or bug in the recipient mail server can cause the email account to get disabled and mails to that account to fail.

If the recipient doesn’t have the email address that you’re sending to, it will bounce the mail with the error message ‘550 5.1.1 User unknown‘.

Solution:

Always validate send mail error 550 user unknown error smart serial number email address you’ve given in the email for any spelling mistakes or errors. If everything is fine at your end, confirm whether the email account actually exists.

[ Are your websites helping you get business? Our website support team gives you custom website solutions and fix all errors in your website in no time. ]

2. Incorrect DNS settings for the domain

Email Error 550 can also occur when the DNS settings for the recipient domain are not correct or the MX entry is not resolving correctly.

For instance, the MX records for the domain could be wrongly resolving to the recipient mail server instead of its intended server.

In such cases, recipient mail server cannot find the account and will bounce the mail. DNS issues can also occur due to any wild card DNS or SPF entry that is not set correctly.

These DNS related errors or wrongly mail server MX settings can end up giving an error message ‘550 5.1.1 User unknown‘ to the sender.

Solution:

Verify the MX records for a domain, using the command:

dig domain.com MX

If you notice DNS errors or missing MX send mail error 550 user unknown, then contact the recipient server support and get it fixed.

3. Email filters set for the domain

Some recipient mail accounts can have email filters or forwarders set. A catchall address or forwarder that relay to a non-existing account, can end up causing 550 errors.

Filtering for incoming mails using email filters or anti-spam firewalls, qc ole error end up bouncing emails from certain sender servers, returning a 550 error message.

Though 550 errors are usually related to recipient mail server issues, at times some filtering or firewalls applied on outgoing mails in the sender server can also cause this error.

For instance, some programs such as Google Apps modify the ‘To address’ of outgoing mails. Updating the recipient address to a non-existing address, can show error ‘550 5.1.1 User unknown‘.

Solution:

Check your outgoing firewalls and rules, if any. If all good, contact recipient server support and get the email filters verified for any erroneous filters or rules that can be blocking mails.

[ A single misconfiguration may break your site! Click here for a customized and error-free website to help you boost your business. ]

4. Mail server configuration errors

Apart from the above reasons, some configuration mistakes in the mail server can also end up causing the error 550 for domains in it.

A server-wide custom filter that blocks mail from certain senders, a default forwarder that relay mails to another address, custom email software or security restrictions, all can lead to email errors.

Sometimes, the issue may be a temporary one. In those cases, the sender mail server will re-attempt the delivery of failed emails, send mail error 550 user unknown, based on its configuration.

Solution:

Examining the error logs and email headers of the bounced mail would help identify the issue with the mail server. Testing email routing in the server would also help detect any issues.

Disabling unwanted filters and rules and ruling out any restrictions that cause the emails to bounce, is crucial in fixing the issue.

550 5.1.1 Error: Detailed Instructions for Fixing It

An SMTP session consists of back-and-forth communication between the client and the server. The client uses text commands and the server replies in numerical codes attached with messages. We discussed this communication in our blog post on SMTP Commands and Response Codes. Error codes can have different meanings on different servers, so you have several potential options for resolving the issue. Today we’ll discuss one of them, error, and explain how to fix it.

What does 550 5.1.1 error mean?

The client typically receives a code as a reply to command. It is an error code that usually stands 2 times terror - d.e.a.d some issue with the recipient server. The most frequent error message is “”. In most cases, this is because the recipient address does not exist. But there are other possible reasons and other possible error messages. 

550 5.5.1 error messages you can encounter

Bonus:

You may see this error message if the outgoing email was rejected. In this case, it is identifying an issue with a sending server that has used SMTP protocol instead of ESMTP. So, send mail error 550 user unknown, does this mean that error code can be caused by issues with both the recipient and sending server? Let’s find out.

Reasons for 550 5.1.1 and solutions 

The basic reason for SMTP error is a typo in the recipient’s email address, such as a missed or duplicated character, resulting in an invalid address. So, email validation should be the first thing to verify. If the email address is valid, you will need to dig deeper.

Issues related to the receiving server

Email address does not exist

  • Check the email address for spelling errors.

MX record resolving to the wrong server

  • Check the routing and DNS resolution.
  • Contact the recipient server administrator to edit DNS records and set up correct MX records.
  • Use Telnet to connect to the receiving server.
  • If connection fails, the email may be blocked by the recipient server.
  • Explore possible issues on the sending server.

Issues related to the sending server

  • Using a dedicated tool, check to see if the Error 017 samp address is blacklisted.
  • Examine email logs for spamming activity.
  • Check the server for malicious scripts.
  • Block any suspicious email account and strengthen password security.
  • Follow the blacklist-removal process.
  • Check DNS records including rDNS, SPF, DKIM, and DMARC.
  • Set up records that will ensure that IP addresses really belong to the domains they claim.

What might be wrong on the receiving end

Email address does not exist

The recipient server can’t find the email account to which you’ve sent an email. Therefore, the email will bounce back to the sender because it cannot be delivered.

How to solve this?

All you can do is recheck the email address for spelling errors. 

MX record resolving to the wrong server

A Mail Exchange (MX) record is a DNS record used by mail servers to determine send mail error 550 user unknown to deliver an email. The sender mail server looks for the MX record in order to communicate with the recipient mail server. The MX record points to the A record which, in turn, points to the mail server’s IP address. For example, the MX record of the domain example.com points to the A record of mail.example.com, which points to 192.168.123.4. If the MX record for the recipient domain resolves to some other server, you can get 550 5.1.1 error. The email delivery fails because the receiving mail server cannot identify the email account in it. 

How to solve this?

First, you need to check the routing and DNS resolution using the tool with the parameter. For example:

The domain should resolve to the correct server on your end. After that, confirm the MX records for the domain using:

If you find any issues, contact the recipient server administrator to edit the DNS records and set up the correct MX records. The MX won’t resolve correctly if the DNS settings for the recipient’s domain are incorrect.

Custom security settings

It’s unlikely that a recipient server has no send mail error 550 user unknown mechanisms to protect from spam. If you get a error message, your email might have been rejected by spam filters. It does not mean that you’re a spammer or your email is spammy, send mail error 550 user unknown. Usually, strict security rules are in the way.

How to solve this?

Use telnet to connect to the receiving SMTP server (or its IP address) to check whether the firewall is blocking the sending server. We blogged about this in How to Test SMTP Server. Run the following:

or 

If telnet says that you can’t connect, it means the recipient server has blocked your emails. So, the reason for the error is much closer to home – on the sending server.

What might be wrong on the sending end

Above we learned that the email sent from your server hit spam filters on the receiving end. There are a few reasons for that. 

Blacklisted IP

Here is how it looks. Some companies monitor servers and blacklist them if they are identified as spam senders. The majority of mail servers refer to these blacklists and reject emails coming from them. If you get error code, your server is likely on such a blacklist. Keep in mind that the use of a shared IP address increases the probability of being blacklisted. If you use a dedicated IP and are blacklisted anyway, your server was likely hacked.

How to solve this?

The first thing to be done is to check whether your IP is blacklisted. You can use such tools as IP Reputation Monitor by GlockApps, send mail error 550 user unknown, Blacklist Check by MXToolbox, or any other you like, send mail error 550 user unknown. After that, you need to follow the blacklist-removal process. Usually, it is based on the requirements of a particular blacklisting database.

Holders of dedicated Cmd error 1275 should examine their email logs for spamming activity. You also need to check the server for malicious scripts. After that, block the suspicious email account and strengthen your password policy. And don’t forget to change the password, of course.

Configuration issues

Another spam trigger refers to improper verification of the sending server. This refers to the verification of TXT DNS records (SPF, DKIM, and DMARC) and the reverse Oki c8800 fatal error record (rDNS). If you get a rejection, the DNS settings might be misconfigured.

How to solve this?

  • Perform a rDNS lookup manually with a command line using the command-line tool (in OSX and Linux) with the added flag lie as follows:

The full rDNS record will be shown in the “” of the outcome. The record must be set up and valid. You can also make use of online tools to verify rDNS:

Reverse DNS Lookup by WhatIsMyIP.com

Reverse DNS Lookup by iplocation.net

Reverse Lookup by MXToolbox

  • Check the TXT records for your domain. This can be done manually using dig send mail error 550 user unknown follows:

and then 

is your name server, which you can find in the “” of the outcome to

  • Also, you can use as follows:

You’ll then need to find the SPF record that starts with. For example:

  • Update it according to your requirements. If the SPF record does not exist, make sure to create one. For more on this, read SPF Explained. 
  • Look for the DKIM record of your emails that starts with. You can validate the DKIM signature using an online tool like DKIM Record Check. For more on this, read DKIM Explained. 
  • Also, you need to look for the DMARC record that starts with. The receiving server always looks for it, send mail error 550 user unknown. If it is missing or is modified in any way, the whole verification will fail. For more on this, read DMARC Explained. 

All DNS records should be set up in a way to show that an IP address indeed belongs to the domain it claims. Otherwise, the recipient server may think that it is using someone else’s domain to send spam emails. You can read more about this in Why Emails Going to Spam and How to Prevent It. 

How to fix 550 5.1.1 user unknown in Exchange, Exim, Postfix and Qmail servers

For Microsoft Exchange Servers

Security parameters are the main reason for error ‘’ in Exchange Servers 2010 and later. They authenticate the sender to prevent spamming and restrict email sending by default. All emails sent beyond local email addresses send mail error 550 user unknown bounced back with the error. Remove the restriction as follows:

  • Go to the Exchange admin center and navigate to Recipients > Mailboxes
  • Click the mailbox for which you want to set up mail forwarding
  • Click Mailbox Features on the mailbox properties page
  • Under Message Delivery Restrictions, select View details to view or change the delivery restrictions 
  • Clear the checkbox Require that all senders are authenticated. Click OK and then Save.

For Exim servers

For Exim mail servers, is not a common issue. But if it happens, send mail error 550 user unknown, the route likely needs to be identified. First, make sure that the mail server settings are correct. Then, verify filters and custom rules added to the server. This will help you identify and fix the .

For Postfix and Qmail send mail error 550 user unknown with the verification of the recipient domain resolution. It must resolve to the correct server. If the email service for the domain is hosted elsewhere, turn it off. Verify filters and custom rules added to the server. They must not mess up the mail delivery.

Can I avoid 550 5.1.1 when sending bulk error lnk1561 entry point must be defined is a nightmare for any marketer who deals with bulk emails. Why? Just imagine that your email campaign has thousands of recipients. If you failed to verify all of them, it’s most likely that a large number of email addresses are invalid. This entails multiple bounces with. Will this have some sort of effect on email hosting providers? What do you think? Of course, it will, send mail error 550 user unknown, and your client will most likely be identified as a spammer sending emails to unverified addresses. 

You might have guessed that there is only one way to avoid this failure – keep your mailing lists clean. For this, you need to make sure that email address validation is a high-priority task. You can easily automate the process using bulk email verifiers available on the market. Some of them we’ve already introduced in the Email Testing Checklist. 

To wrap up

As you can see, is not an unsolvable issue. Be attentive to your server settings and do not neglect email address verification. By following these steps, you won’t jeopardize your email campaign. additionally, it’s advisable to test your emails for spam, and Mailtrap can help you with this. Mailtrap is a service for sending test emails via SMTP and also has features for email content verification and debugging. You can’t have too much of a good thing. For more on what else this service offers, read the Mailtrap Getting Started Guide.

Article byZakhar YungTechnical Content Writer @Mailtrap

Resolving Error Messages


Cause:

When reads from any source that might time out, such as an SMTP connection, the program sets a timer to send mail error 550 user unknown value of various options before reading begins. If the read is not completed before the timer expires, this message appears and reading stops. Usually, this situation occurs during. The mail message is then queued for later delivery.

Solution:

If you see this message often, increase the value of various options in the file. If the timer is already set to a large number, look for hardware problems, such as poor network cabling or connections.


Cause:

This message indicates that the destination host machine, which is specified by the portion of the address after the at sign (@), was not found during domain name system (DNS) lookup.

Solution:

Use the command to verify that the destination host exists in that domain or other domains, perhaps with a slightly different spelling. Otherwise, contact the intended recipient and ask for a proper address.


Cause:

This message indicates that the intended recipient, who is specified by the portion of the address before the at sign (@), could not be located on the destination host machine.

Solution:

Check the email address and try again, perhaps with a slightly different spelling. If elfinder 500 internal server error remedy does not work, contact the intended recipient and ask for a proper address.


Cause:

This message usually indicates that the local host is trying to send mail to itself.

Solution:

Check the value of the macro in the file to ensure that this value is a fully qualified domain name.

Description:

When the sending system provides its host name to the receiving system in the SMTP command, the receiving system compares its name to the sender's name. If these names are the same, the receiving system issues this error message and closes the connection. The name that is provided in the command is the value of the macro.

For additional information, refer to .


Cause: send mail error 550 user unknown error message occurs if you set up an MX record and make host the mail exchanger for domain. However, you fail to configure host to know that it is the mail exchanger for domain .

Also, another possibility is that both the sending system and the receiving system are identifying as the same domain.

Solution:

For instructions, refer to .


Description:

This is an old message, which replaced and is now replaced by the message.

Solution:

Follow the instructions that were provided for resolving this error message, send mail error 550 user unknown.


Cause:

When you try to send mail to a user, the error is displayed. The user is on the same system.

Solution: send mail error 550 user unknown for a typographical error in the entered email address. Otherwise, the user could be aliased to a nonexistent email address in or in the user's file. Also, check for uppercase characters in the user name. Preferably, email addresses should not be case sensitive.

For additional information, refer to .

send mail error 550 user unknown

1 Comments

Leave a Comment