What does error 550 mean when I try to send emails?

The 550 Email error, is related to the SMTP protocol and is commonly associated with recipient-side errors.

Below, we present the error codes and their meanings:

1. Email Error 550 5.1.0 Address Rejected. Address rejected. This error message means the recipient’s server will not accept emails from you. This is likely because the recipient is blocking your email address.

2. Email Error 550 5.1.1. Means the recipient email address you entered is invalid or does not exist on the destination domain. This occurs due to typos in the email address or incorrect configuration of the recipient’s server.

3. Email Error 550 Denied By Policy. Means an email security software has blocked outgoing emails to prevent attackers from guessing addresses by sending randomly generated email addresses.

4. Email Error 550 5.4.1.

   Means the recipient’s server does not accept emails from the domain you are using. Usually this error occurs due to incorrect DNS configuration.

5. Email Error 550 5.7.0 Message Size Violation. Message size violation. This error occurs when your email contains a file that exceeds the allowed size limit.

6. Email Error 550 5.7.1 Access Denied. Means the email was rejected due to security policies or incorrect configuration on the recipient’s side.

7. Email Error 550 Administrative Prohibition. It can mean any of the following:

   • The domain used by your SMTP server is on real-time blacklists.
   • The recipient uses a domain that is on real-time blacklists.
   • The SMTP server has a dynamic IP address.

8. Email Error 550 Relay Not Permitted. Means the recipient’s server does not allow the server you are using to send the email.

9. Email error 550 Quarantined / 550 Error Recipient Quarantined. Means your email was marked as spam and was not delivered. You will also face the same error message if your email address is on a blacklist.

10. Email error 550 SPF. A mail server will check a domain’s Sender Policy Framework (SPF) record to verify whether a sender is valid or not. If you send email from an IP address that is not registered in SPF, you will receive this error message.

11. Email error 550 reverse DNS. Means there is no reverse DNS record for the mail server’s IP address or there is a record mismatch on the domain used to send the email.

12. Email error 550 recipient unknown / no such user here. Means the recipient’s mail server cannot find the email account. This can occur due to typos in the email address.

13. Email error 550 host unknown. The SMTP server sends this message if the hostname specified in the email address is unknown.

14. Email error 550 Authentication is required for relay. Means Simple Mail Transfer Protocol (SMTP) authentication is missing. To send outbound mail, SMTP authentication must be enabled in your email client, with your username and password.

15. Server error 550 or 550 Blocked Error. This error message appears when the recipient’s mail server blocks the mail you are trying to send. This SMTP error code indicates that the email will be bounced back to the sender.

16. Error 550 5.1.0 Address Rejected. Indicates that the recipient’s server does not accept emails from the sender (you) or messages to the recipient. This error appears if the email address or all Exchange Online emails are blocked by the recipient.

17. Server error 550 this domain is not hosted here. This is another common error. The server rejects the sent mail when the recipient’s username cannot be found or is not accessible. Other reasons include typos in the email address and MX records.

18. Error 550 in Outlook. This error message is frequently associated with “550 Authentication is required for relay.” It means your mail server requires SMTP authentication to send emails, but the email client you are using has not yet authenticated with your username and password.

Possible solutions to the issues:

• Check for typos in the email address. The 550 email error can occur due to typos in an email address. Make sure the email address you entered is correct and does not contain extra spaces or spelling mistakes. There is also the possibility that the recipient gave you an incorrect email address. Confirm it with them as well.

  Also, verify that your email address was entered correctly and that your email has content. Some mail servers will reject an email that has no content.

• Check if your email IP is on a blacklist If your email IP is on a DNS blacklist, most of your emails will not reach the recipient and will be rejected.

• Try changing the mail sending port If your email application uses port 25 as the mail sending port, servers may block the mail since spammers often use port 25 to send unwanted messages. Try changing the port to 26, 465, 587 or 2525.

• Check if IP filtering is enabled Your SMTP server may be configured to authorize users only from a specific set of IP addresses. If that is the case, you will not be able to send messages from other locations. You can resolve this quickly by contacting your mail server administrator.

• Enable SMTP authentication In most email applications, SMTP authentication is configured automatically. If the application does not configure it correctly, you will not be able to send emails. Fortunately, you can configure SMTP authentication manually.