Perhaps it's standard but we needed a way to turn the SPAM filtering on and off for certain users.

The whole problem comes down to the owner of this mail server not wanting to invest in more (faster) hardware. It's running on a decent box (that is pushing 6 years old) but this mail server handles incoming and outgoing mail and can deliver as many as 10,000 messages per hour, 400 or so domains and 500+ users hitting IMAP/POP3 every few seconds.. SpamAssasin is bloody slow, really bloody slow, and it was bringing the box to it's knees at peak time trying to filter every piece of mail going through the server. I changed the filtering from within postfix to maildrop so we could easily turn it on and off per user..

I read several places that filtering through maildrop is actually faster anyway, but we're not doing near the filtering these days (since SA is turned off for most users) so I can't really tell if it's faster under the same conditions...

Thanks for the comments! Any other ideas as to what/why this flock thing is happening?

I have the destination_concurrency_limit in postfix to 1, so it should never try to deliver more than one piece of mail at a time per user (well, I think!)..

--Mitchell