Postfix maillog delays

The joys of troubleshooting postfix maillog delays!

When postfix is experiencing delays in delivering emails, it can be frustrating and impact the reliability of your email service. Here are some common issues and their corresponding error messages in the postfix maillog that may indicate delays:

  1. Connection timeouts:

    connect to <domain.com> [<IP address>]:25: Connection timed out

    This error indicates that postfix is unable to establish a connection to the remote mail server within the specified timeout period. Check your network connectivity and firewall settings to ensure that postfix can reach the remote server.

  2. Authentication issues:

    authentication failed for <username> (<domain.com>)

    This error indicates that postfix is unable to authenticate with the remote mail server. Check your authentication settings, such as username and password, and ensure that they are correct.

  3. DNS resolution issues:

    lookup <domain.com>: getaddrinfo failed: Name or service not known

    This error indicates that postfix is unable to resolve the domain name to an IP address. Check your DNS settings and ensure that the domain name is correctly configured.

  4. Mail queue issues:

    deferring delivery of <email address> (message too large)

    This error indicates that the email is too large to be delivered and is being deferred. Check your email size limits and consider increasing them if necessary.

  5. Recipient address issues:

    unknown user: <recipient email address>

    This error indicates that the recipient email address is not valid or does not exist. Check the recipient's email address and ensure that it is correct.

  6. Mail server issues:

    remote server returned error after DATA command: 421 <error message>

    This error indicates that the remote mail server returned an error after receiving the email. Check the remote mail server's logs and configuration to identify the issue.

To troubleshoot postfix maillog delays, you can try the following:

  1. Check the postfix maillog for errors and warnings.
  2. Verify your network connectivity and firewall settings.
  3. Check your authentication settings and ensure that they are correct.
  4. Verify your DNS settings and ensure that the domain name is correctly configured.
  5. Check your email size limits and consider increasing them if necessary.
  6. Verify the recipient's email address and ensure that it is correct.
  7. Check the remote mail server's logs and configuration to identify any issues.

By following these steps, you should be able to identify and resolve the cause of the delays in your postfix maillog.