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Date:      Tue, 14 Oct 2003 23:47:12 +0100 (BST)
From:      Jethro R Binks <jethro.binks@strath.ac.uk>
To:        freebsd-stable@freebsd.org
Subject:   Re: Spamassasin
Message-ID:  <20031014232435.L64920@defjam.cc.strath.ac.uk>
In-Reply-To: <1066164638.6688.5.camel@hawk.gnome.co.uk>
References:  <20031012123823.M25378@littlejack.nl> <200310121213.34769.wes@softweyr.com> <20031014115902.GA25582@rfc-networks.ie> <1066164638.6688.5.camel@hawk.gnome.co.uk>

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On Tue, 14 Oct 2003, Chris Stenton wrote:

> On Tue, 2003-10-14 at 12:59, Philip Reynolds wrote:
> >
> > Mailscanner seems like a very poorly designed piece of software, at
> > least from my experience with Postfix.
> >
> > It directly manipulates the Postfix queue which can cause message
> > corruption. This has been raised on the Postfix list recently and
> > since Wietse & co. have been advising _against_ using it with
> > Postfix.
>
> Interesting. I still use sendmail (with check_local) and it seems OK
> with that but it is setup to use an in and out queue.

MailScanner was originally written to interface with sendmail, using an
in-queue and an out-queue mechanism.  Sendmail's queue files are well
documented.  Exim support came shortly after, Exim being architecturally
very similar to sendmail.  Again, there is good documentation for the
queue format, and its queue handling is robust.

Exim/sendmail+MailScanner combinations are used extensively in the UK
academic community to good effect.  Those close to Exim's author use
Exim+MailScanner, and advice on one way of integrating Exim+MailScanner
was written by Exim's author.

MailScanner's design is pretty simple: it expects the SMTP daemon to place
incoming mail in a queue, and do nothing more with it.  MS will process
messages in that queue, and when done launch an outgoing mail process to
deliver it or place messages in an outgoing queue for an MTA to read.  It
handles locking and such like, and makes sure that messages are not
finally removed from the incoming queue until they have been fully
processed and submitted for onward delivery.

Postfix support was only fairly recently added after repeated requests.
I've heard that the queue format is less clearly documented (I don't know;
I don't use postfix).  I also understand that the Postfix developers
prefer other programs not to mess around with the Postfix queue directly.
Whether MS does so robustly or not I couldn't say: best ask someone who
runs Postfix+MS.  If Postfix's developers are unhappy with the way that MS
does so, then I guess it isn't surprising that they would advise against
using MS.  MS' developers strive for robustness, so if the information is
readily available on how to safely access the Postfix queue they will
probably have taken it into account.

Speaking personally, MS has saved us time and time again from email-bourne
threats over the past couple of years, and allowed us to implement a
fine-grained mail security policy that is customisable on a per-user basis
if necessary.  No other AV solution offers even half the features and
configurability that MS does, and MS now scans and protects huge amounts
of mail in many many installations.  Our site was protected from
Sobig.whatever before the thing was even released, without needing to wait
for AV definitions to be updated.

Just felt that a little defence of MS was necessary.

Jethro.

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Jethro R Binks
Computing Officer, IT Services
University Of Strathclyde, Glasgow, UK



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