daniel wrote:
My boss wants me to create a bunch of mail relays to capture and relay mail
sent to us and discard spam etc, but I'm not sure where to start. I'd like
to use exim unless you all have a better idea. To be honest, at the moment,
I'm not sure where to start.
Here's a simple diagram that might help you understand what it is we want to
do (fixed width font will help):
[SMTP] [SMTP] [SMTP] [SMTP]
| | | |
+---------+----+---+---------+
|
[SMTP+POP3]
Each of the SMTP servers have different routeable IPs and are linked together
via a RoundRobin DNS. Their sole purpose would be to check mail being sent
to them against a list of known users @ourdomain.com and possibly filter spam
as well. Messages that satisfy the filter would then be forwarded to the
main mail server where we would all pick up our mail with our various email
clients.
So at the moment, my main issues are:
- How do I replicate the user list from the master to the satellites?
- What MTA should I use on the satellites and how would I configure it?
I am assuming (from the 4 smtp servers) that you have at least
several hundred users, who receive lots of email. That being
said, surely you must be using LDAP. As to the MTA, well pick
your poison. I'm a Sendmail guy, but that's just me.
My first thought is that your first line of defense should be
a bank of smtp servers that know nothing of your internal users.
The first line of defense should be focused on virus detection,
adherence to SMTP protocols and RFCs, greet-pause, listing
(black, white and grey) and my personal favorite, the tar-pit.
Only mail that gets past the first line of defense gets to a
SMTP server that knows or cares about user account names.
And another thing, if your company is as large as it should
be to justify 4 outside STMP servers, why would you be using
pop? Use IMAP (and probably Maildirs) so mail can be backed
up to tape and not scattered across hundreds of workstations.
Just my first thoughts, based on no actual knowledge of your
environment.
Best,
Ray
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