From: Bill Cole (postfixlists-070913billmail.scconsult.com)
Date: Thu Dec 06 2007 - 10:24:50 CST

• Messages sorted by: [ date ] [ thread ] [ subject ] [ author ]

At 10:25 PM -0700 12/5/07, utahnix wrote:
>Pardon me if I'm asking a lot of the same questions. I'm not trying
>to be a pain.
>
>Is there a way to have Postfix reject a message upfront (during
>SMTP) if the MUA reports it is undeliverable (quota, or perhaps the
>MUA is down for some reason), so that the message isn't queued?

Terminology problem already noted; MDA, not MUA.

As far as I know, Postfix does not provide any way to latch
acceptance of mail to synchronous delivery (as can be done with
Sendmail) and I would guess from Dr. Venema's discussions of related
issues that this is a matter of his design principles for a robust
mail system.

*In principle* the ways to hook into Postfix before it accepts and
queues a message are the milter, policyd, and smtpd_proxy interfaces.
How *you* could use those to check your deliverability depends on the
unspecified details of your system, particularly how you can check
quota status. You'd need to look to the MDA (Cyrus in your case?) for
the tools for determining that status without trying delivery, and
decide what path to take in hooking message acceptance. Note that by
doing this, you make acceptance dependent on something running
external to Postfix, so it can reduce reliability.

Victor's suggestion of using an access map that is updated
asynchronously to reflect deliverability status is also a great
approach if you can trade theoretical perfect correctness at all
times for greater practical performance and robustness. If I remember
Cyrus correctly, there's a tool that can check all quotas which could
be used to periodically generate an access map to reject mail to
recipients who are over their quotas.

--
Bill Cole
billscconsult.com

• Messages sorted by: [ date ] [ thread ] [ subject ] [ author ]