When sending emails from the command line using utilities like mail, mailx, or sendmail, troubleshooting can involve several steps to ensure that the email is sent properly and to diagnose any issues with email delivery. Here’s a comprehensive guide on how to trace and troubleshoot email sending on Unix-like systems:

1. Check the Command Syntax

First, ensure your command syntax is correct. Check for any typos or incorrect usage of options. Refer to the manual pages (man mail, man mailx, man sendmail) to confirm you are using the correct options.

2. Verify Configuration Files

Email command line tools often depend on configuration files like /etc/mail.rc, ~/.mailrc for mail or mailx, and /etc/sendmail.cf for sendmail. Check these files to ensure they are configured correctly, particularly settings related to SMTP servers, authentication, and default headers.

3. Send Test Emails

Send test emails to confirm the functionality of the command:

$ echo "This is a test email" | mail -s "Test Email" devops@rajeshkumar.xyz


Change recipient@example.com to a real email address where you can check the inbox.

4. Check Mail Queue

If you’re using sendmail or a similar MTA, you can check the mail queue to see if your message is stuck:

$ mailq

or for Postfix:

$ postqueue -p

5. Review Mail Logs

Mail logs can provide detailed info about what happens when you try to send an email. Check the logs to see if there are any errors or status messages about your emails:

bashCopy code# For systems using syslog
grep mail /var/log/syslog

# For systems using journalctl (systemd)
journalctl -u postfix

# Check sendmail logs
grep mail /var/log/maillog

6. Use Verbose Mode

Some mail commands allow you to see what happens step-by-step by using a verbose option:

bashCopy codeecho "This is a test email" | mail -v -s "Test Email" devops@rajeshkumar.xyz

The -v option can show you the SMTP dialogue which can be very revealing.

7. Ensure Network Accessibility

Check that your system can reach the SMTP server specified in your configurations:

$ telnet smtp.server.com 25
$ telnet alt1.aspmx.l.google.com  25
Trying 173.194.202.27...


Replace smtp.server.com with your SMTP server and 25 with the appropriate port number if different.

8. Test with Alternative Tools

If mail or mailx is not working as expected, try using sendmail or another tool like ssmtp or msmtp for sending a test email to check if the problem is specific to a tool or a broader configuration or network issue.

9. Validate Email Headers

Ensure that the email headers, especially ‘From’, ‘To’, and ‘Subject’, are correctly formatted. Incorrect headers can cause emails to be rejected or marked as spam.

10. Consider Anti-Spam Measures

If your emails are being sent but not received, they may be blocked by spam filters. Ensure your server is not blacklisted, and consider setting up SPF, DKIM, and DMARC records to improve your email deliverability.