[CentOS] company exchange server & exim best practices.

Fri Apr 3 07:40:44 UTC 2009
Rudi Ahlers <rudiahlers at gmail.com>

Hi all,

I hope this isn't too OT, but since I use a CentOS5.2 + Exim mail
server (which is hosted in one of our data centres) I don't think it
should be.

On of our clients use an MS Exchange 2003 SBS server, with exchange
for their internal email. We provide them with a domain, ADSL (which
uses dynamic DNS) and POP3 email. They don't have an spam filter
program on the exchange server itself due to costs, so I have setup
each user on the Exim server, which runs ASSPX for anti-virus / spam
filter / etc. Then I setup the SBS 2003 server to pull the email via
POP3, but this doesn't seem to work too well, cause the exchange
server doesn't always download the POP3 email, and then the users
often sit without email until I go there to manually download the mail
again.

I have tried changing the MX record to point to their DynDNS address,
and it works well, but then they get a lot of spam. And the cost of a
server-side spam solution is just too expensive, and they also pay for
the bandwidth uses when spam comes in. So, I moved their MX record
back to the Linux server. But now I sit with the problem of the POP3
connector failing from time to time.

So, I would like to know, is there a way to "push" (not forward) mail
from the Linux server, after it has arrived and spam been blocked, to
another domain, but with the same email address? i.e. the domain in
question is attorneys.co.za and I've setup attorneys.dyndns.net as the
dynamic domain, but the exchange serves email for attorneys.co.za
Forwarding email doesn't work, since there's no such user as
bob at attorneys.dyndns.net, but rather bob at attorneys.co.za.

-- 

Kind Regards
Rudi Ahlers