Hi Ferguson,, on Fri, 19 Dec 2003 14:36:54 -0500 you wrote:
> Sometime ago I read where someone had setup an Exim Server with Spam
> Assassin in front of an Exchange 2000 server and was quite successfully
> stopping spam, worms viruses, etc. Can someone tell me more about this
> or point me to documents.
OK, first off, you can achieve this with any backend mailserver by setting
up a frontline server with Exim on plus whatever spam/virus scanning you
want. Many of us block huge amounts of spam through various methods using
Exim; whether it's being passed to "backline" servers or delivered to user
mailboxes doesn't really affect things much (other than that in the former
case you want to do recipient checking, which I'll mention in a minute).
Now, I'll talk you through some of the basic techniques but won't go into
precise details since I don't know how much you know about Exim. If you've
never used it before then welcome; the things mentioned here might sound
unfamiliar and scary but don't worry, once you start to use it with the
manual to hand, things will fall into place. I'm assuming a basic
knowledge of SMTP in either case.
On the first line of spam defence (just checking where mails are coming
from at SMTP RCPT time), you need to investigate DNSBLs and decide which
ones you want to use; I recommend at least sbl.spamhaus.org and
list.dsbl.org.
Also at SMTP RCPT time, you want to check the destination usernames
presented are valid, so you don't end up with frozen spam on your queues
and "collateral-spamming" innocent third parties. Because Exchange is a
big heap of stinking crap, it doesn't reject recipients at SMTP time,
which makes your life that bit harder (otherwise you could just do an SMTP
callout to the Exchange server to verify that the recipient exists).
However, IIRC there is a recipe in the Exim cookbook on exim.org which
will let you check recipients against an Exchange LDAP user database, so
you should be able to use that.
For the second line of defence (checking content for spam/viruses), I've
written a guide which is at
http://www.timj.co.uk/linux/exim.php talking
you through the options and how to set it up.
Finally, to send accepted mail to your Exchange (or whatever) server, add
a "manualroute" router at the head of your routers list which redirects
the mail to the Exchange server, something like this:
scan_domains:
driver = manualroute
domains = brvmlaw.com
route_data = your.exchange.server.hostname
transport = remote_smtp
no_more
(you could obviously expand this to cope with multiple domains and/or
multiple backend servers).
Hope that helps.
Tim
P.S. Truly awful "website" (aka downloadable binary application) your
company's got, by the way...
