What is "mail server traffic" and how to analyze email sending and receiving logs?

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Mail server log analysis is a fundamental skill for system administrators and developers responsible for the uninterrupted delivery of correspondence. Logs contain a detailed chronology of all connection attempts, authorization, and the successful or unsuccessful delivery of each individual message.

The primary tool for reading such logs on Linux systems with popular Mail Transfer Agents (MTAs) like Postfix or Exim are system log viewing utilities, including the tail command and filtering tools like grep. Each entry contains a unique message identifier, sender and recipient IP addresses, and the operation execution status.

For effective log analysis, it is useful to follow a specific algorithm:

1. Determine the unique identifier of the problem email or the recipient's email address.
2. Filter the log lines by this identifier using the grep command to track the entire path of the message from sending to the final response of the remote server.
3. Pay attention to status codes and text error messages, such as 550 Relay Access Denied or Connection Timed Out.
4. Correlate timestamps with network issues or DNS service failures.

Regular monitoring allows you to timely detect unauthorized access attempts to the server, as well as promptly respond to IP address reputation problems. Automating this process using log aggregation systems helps minimize infrastructure downtime.

Understanding the log structure makes it possible to quickly localize the problem and restore the normal flow of incoming and outgoing mail without wasting extra time.

What is "mail server traffic" and how to analyze email sending and receiving logs?

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