Mail duplicate delivery in qmail

SYMPTOMS

You have two (or more) copies of every message sent/received from/to your qmail system.

CAUSE

Most probably you have two (or more) qmail instances running.

RESOLUTION

Verify that you have only one qmail instance running. To do this, login to the mail server and run:

# ps -ax | grep qmail-send

If you see two (or more) processes, stop qmail and verify it is stopped:

# /etc/init.d/qmail stop
# ps -ax | grep qmail

You should see no qmail processes here, each qmail instance would be stopped by this command.
Now it is safe to start qmail:

# /etc/init.d/qmail start


Only one copy should be started.