Postfix mail logs

Postfix is a popular open-source mail transfer agent (MTA) that is widely used on Linux systems. Postfix logs can be used to troubleshoot email delivery issues, monitor email traffic, and detect potential security threats. Here are some common postfix mail logs and their meanings:

Main Log Files

Postfix logs are stored in the /var/log/mail.log file by default. You can also configure postfix to log to other files or destinations.

Common Log Messages

Here are some common postfix log messages and their meanings:

1. Delivery Status

< postfix@server >: 250 2.1.5 Recipient OK

• This message indicates that the email was successfully delivered to the recipient's mailbox.

< postfix@server >: 550 5.1.1 Recipient address rejected: User unknown in local recipient table

• This message indicates that the email was rejected because the recipient's email address is not recognized by the local recipient table.

2. Connection Establishment

< postfix@server >: connect from unknown[IP address]

• This message indicates that a new connection was established from an unknown IP address.

< postfix@server >: disconnect from unknown[IP address]

• This message indicates that a connection was closed from an unknown IP address.

3. Authentication

< postfix@server >: authentication failed for [email protected] from unknown[IP address]

• This message indicates that an authentication attempt failed for the specified user from an unknown IP address.

< postfix@server >: authentication successful for [email protected] from known[IP address]

• This message indicates that an authentication attempt was successful for the specified user from a known IP address.

4. Relaying

< postfix@server >: relay access denied from unknown[IP address]

• This message indicates that a relay attempt was denied from an unknown IP address.

< postfix@server >: relay access granted for [email protected] from known[IP address]

• This message indicates that a relay attempt was granted for the specified user from a known IP address.

5. Error Messages

< postfix@server >: fatal: open /var/spool/postfix/public/maps: Permission denied

• This message indicates that postfix was unable to open a file due to permission issues.

< postfix@server >: fatal: unable to create pid file: Permission denied

• This message indicates that postfix was unable to create a pid file due to permission issues.

Analyzing Log Files

To analyze postfix log files, you can use various tools and techniques, such as:

1. grep: Use the grep command to search for specific patterns in the log files.
2. logrotate: Use the logrotate command to rotate and compress log files.
3. postfix log analyzer: Use a dedicated log analyzer tool, such as postfix-log-analyzer, to analyze postfix log files.
4. syslog-ng: Use a syslog server, such as syslog-ng, to collect and analyze postfix log files.

By analyzing postfix log files, you can troubleshoot email delivery issues, detect potential security threats, and optimize postfix configuration for better performance.