Re: [gentoo-user] [OT] opinions & know-how requested: how to create a mail cluster

[kashani]

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 don't even know if "cluster" is the right word since whenever I google for
> it, i run into references to LVS and Beowulf clustering which is not what I
> need.
>
> Any help and/or opinions/suggestions would be greatly apprecated.
>

I'm a Postfix guy, so these are Postfix How-tos. I'd imagine you can 
probably do the same in Exim or any other MTA with a bit of googling now 
that you've seen the concept.

Creating a recipent table on the front end servers
http://www.unixwiz.net/techtips/postfix-exchange-users.html
	This how-to assume you have a Postfix server that relays to an internal 
Exchange server. Their method isn't super fancy, but does work. You may 
want to look into the LDAP stuff or using a DB query if you store your 
users in one.

http://sqlgrey.bouton.name/
	Greylisting for Postfix. I personally use Postgrey (which is in 
Portage), but will probably switch to sqlgrey at some point in the 
future. Greylisting kills a very large amount of spam before it makes 
into your queues or gets processes by CPU intensive content filters.
	However you MUST have a central greylist backend if you have multiple 
front ends or you'll bouncing mail or have very long delivery times. 
Made that mistake myself.

http://www.postfix.org/docs.html
	Lots of good how-tos here.

http://high5.net/postfixadmin/
	Virtual mail system around Postfix/Mysql/Courier. Includes a very nice 
front end for managing domains, aliases, users, etc. I recently moved my 
old virtual system over to this.
	I'm guessing you already have a smtp/pop3 system and are just looking 
to front end it with some other servers, but thought I'd throw this out 
there anyway.

	I'm curious about how large of system you're planning to have. You may 
want to consider using shared storage with 3-4 servers that all do 
smtp/smtp-relay/pop3/spam filtering/etc. That way you have better 
overall availibility though again that depends on what sort of backend 
you have or are planning to build.

kashani
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