Filtering before MS Exchange

[Tom Allison]

mbox mbarsalou wrote:
> I personally use bogofilter at home and was considering pitching it to
> an organization that is currently using MS Exchange.
> 
> I am fairly sure that they are not wanting to get rid of Exchange, so my
> thinking is gravitating toward using bogofilter in a gateway machine
> that delivers the mail to the Exchange server.
> 
> What are some opinions from the group here?
> 
> Aside from the distaste some might have for MS Exchange, is this a
> viable option?
> 
> If this is a good idea, what should the gateway machine look like?  What
> services need to be on it and what are some good methods for determining
> the required hardware.  I was thinking something like Sendmail,
> procmail, bogofilter.  Alternatives? 
> 
> We take small positive steps toward the light. :)
> 
> Mike B.
> 
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The difficulty is getting bogofilter to work on a mail server without 
the local delivery agent.  Typical application of bogofilter is after 
it's been handled by the mail server and is on it's way to local delivery.

However, you could pitch something like postfix and proxsmtpd might do 
well for this.  I found it on a web page that also has clamsmtpd tools 
that I am using with great success.

I believe that this could allow you to utilize bogofilter as a filtering 
tool.

However, I have to comment that my current mail server, though old and 
"known" to the spammers, is only taking receipt of <10 spams per day 
based on postfix only configuration.  If you could impliment a postfix 
only gateway you might find yourself having a very significant impact 
with a minimum of processing overhead.  It could be a relatively small box?

I have to admit that immediately after implimenting greylisting on my 
mail server, the spam received went from 30-60 to 1-2.  It's now peaked 
at 14 in one day with an average of ~5 per day.  I believe that the 
lesson here is that everything/anything you do to affect spam delivery 
on a mail server will have a great temporary affect with only a modest 
affect in the long run.  I estimate that in 6 months my spam will reach 
highs of 30 again.  But perhaps I'm being pessimistic.