Understanding and Utilizing Mail Logs in Your Linux Server Print

  • 0


Email servers are critical components of any business's communication infrastructure, and monitoring their activity can provide invaluable insights into your email system's health and security. This article will guide you on how to effectively use tools like grep and zgrep to examine mail logs on your Linux server, specifically focusing on Exim, a popular mail transfer agent.

Why Monitor Mail Logs?

Monitoring mail logs can help you:

  • Detect and troubleshoot delivery issues.
  • Monitor for unauthorized access or spam activity.
  • Ensure compliance with business and legal policies.

Accessing Mail Logs

On most Linux servers configured with Exim as the mail server, the primary log file is located at /var/log/exim_mainlog. This log file records every single transaction that Exim handles, providing a detailed trace of all email activities.

Using grep to Search Mail Logs

The grep command is a powerful tool for searching plain-text data sets for lines that match a regular expression. To use grep to search your mail logs:

  1. Basic Search
    To find all instances of a specific message ID or email address, you can use:

To find all instances of a specific message ID or email address, you can use:

grep "search_pattern" /var/log/exim_mainlog

Replace `"search_pattern"` with the term you are interested in, such as an email address or error code.

Case Insensitive Search
Add the -i option to perform a case insensitive search:
grep -i "search_pattern" /var/log/exim_mainlog

Counting Occurrences
To count how many lines match your search pattern, use the -c option:

grep -c "search_pattern" /var/log/exim_mainlog

Using zgrep to Search Compressed Mail Logs

Logs can consume a significant amount of disk space and are often rotated and compressed. The zgrep command works just like grep, but on compressed files. To use zgrep on a compressed log file:


zgrep "search_pattern" /var/log/exim_mainlog-20240505.gz

Example: Searching for Failed Delivery Attempts

To find all failed email delivery attempts, you might search for the status code "N":

grep " N " /var/log/exim_mainlog


This command will list entries where emails have not been successfully delivered.


Understanding how to search and analyze your mail logs is a crucial skill for managing a reliable mail server. By using grep and zgrep, you can quickly identify potential issues or ensure everything is functioning as expected.

Further Assistance

For more detailed guidance or if you encounter any issues, please visit our Knowledgebase or Submit a Ticket for personalized support.

Was this answer helpful?

« Back