dbmail-postfix-policyd is a Postfix policy server for use with DBmail.

Copyright (c) 2005,2011 by Jesse Norell.  All rights reserved.
Copyright (c) 2005,2011 by Kentec Communications,  Inc.  All rights reserved.

dbmail-postfix-policyd was started as a fork of sqlgrey
(carrying over the GNU General Public License), and as such:

Portions Copyright (c) 2004-2007 by ETH Zurich. All rights reserved.

Currently only a Quota Check is performed, allowing some mail to be rejected in SMTP that would otherwise push a user over their quota limits (rather than accepting the mail in SMTP and generating a bounce message). That keeps undeliverable bounce messages out of your local mail queue, and is better net etiquitte.