Mail Queue Troubleshooting (SME Server)

SME Server traditionally uses qmail-style tooling.
If your system is configured differently, adapt as required.

Quick status

qmail-qstat

This gives a high-level count of queued messages.

Read queued messages (carefully)

qmail-qread

Look for patterns:

• same destination domain repeating
• same sender repeating
• lots of bounces

Common causes

DNS problems

If DNS breaks, mail delivery often stops.

Check resolver config:

cat /etc/resolv.conf

Test DNS:

dig +short mx gmail.com

Remote blocking / rate limiting

If a remote server is rejecting messages, the queue can grow.

Look for repeated errors in logs:

grep -i 'qmail' /var/log/maillog | tail -100

Spam burst

A compromised account or open relay misconfiguration can create a flood.

Actions:

• Check authentication logs
• Confirm relay rules
• Review recent send volume

Containment

If you suspect spam, containment comes first:

• stop the source (account / script / system)
• then deal with the queue

After fixing the cause

Re-check:

qmail-qstat

The queue should begin draining.

Notes

Be cautious about deleting queue files directly.
It is usually better to fix the underlying delivery issue and let the queue drain naturally.