Check Mail Queue
# View queued messages
mailq
postqueue -p
# Flush the queue (retry delivery)
sudo postqueue -f
# Delete specific message
sudo postsuper -d MESSAGE_ID
# Delete all queued messages
sudo postsuper -d ALL
Check Mail Logs
# Recent delivery attempts
sudo tail -100 /var/log/mail.log
# Filter for errors
sudo grep -i "reject\|bounced\|deferred\|error" /var/log/mail.log | tail -20
# Check specific recipient
sudo grep "recipient@example.com" /var/log/mail.log
Common Issues
Emails Going to Spam
- Check SPF, DKIM, and DMARC records
- Verify PTR record matches your mail hostname
- Check IP reputation on blocklists
Connection Refused
# Test SMTP connection
telnet mail.example.com 25
# or
openssl s_client -connect mail.example.com:465
Authentication Failures
# Check Dovecot auth log
sudo grep "auth failed" /var/log/mail.log
DNS Verification
# Check MX records
dig MX example.com
# Check SPF
dig TXT example.com
# Check DKIM
dig TXT selector._domainkey.example.com
# Check DMARC
dig TXT _dmarc.example.com