How to disable Mail Service?

I'm running Lion Server 10.7.3. I have no need for the Mail service, so I want to disable it. But it always re-enables itself after just a few seconds.

In system.log I get these messages several times per second.

lda: Error: userdb lookup: connect(/var/run/dovecot/auth-userdb) failed: No such file or directory

lda: Fatal: Internal error occurred. Refer to server log for more information.

I've tried turning off Mail service using Server.app, and also Server Admin. But it always just turns itself right back on. What is going on??