I am about to install Postfix on one of my linux machines in order to act as a gateway for my Exchange servers. I already checked the manpages and searched the forums here, but it didn't provide me with the information I needed.

By default, I just want to forward all mail for a certain domain to Exchange server A, but when needed, I would like all mail for certain users belonging to that domain to go to Exchange server B.

example:

• *@domain.com => Exchange 01
• joe@domain.com => Exchange 02

I also would like to know if it is possible to strip attachments based on extension, using just postfix.

Is this something that can be done? Any examples would be appreciated. Thanks!

I've been looking at how to do something similar to that at my job. We are running Exchange as our primary email server, but it doesn't like making two different aliases point to the same external email address. So I am trying to put Postfix in front of Exchange in the mail flow to act as a relay/filter, and when it finds an address that I know needs to be forwarded to another address, it does a look-up and changes the header, and sends the message on through to Exchange to then be sent back out.

The difficulty I am dealing with is that nowhere have I found documentation that deals with a relay that has no local mail, and can forward addresses. All I can get it to do right now is relay without modifying the header, thus creating a loop.

Anybody know Postfix out there?

--Zerg4141

Might be good to read this.To summarize:

(1) Add the domain in question to relay_domains
(2) List all possible recipients for that domain in a table specified by relay_recipient_maps. This is to avoid possible backscatter from internal mail servers rejecting unknown addresses.
(3) Using transport_maps, define a table specifying Exchange 01 as the domain default, with per-user overrides specifying Exchange 02.

http://freespamfilter.org has some configurations that do what you're looking for. We have an email spam/virus gateway/filter protecting our exchange server, we based our postfix configuration on the Redhat 9 config listed on the web page above. This spamfilter has been in operation for almost 2 years and has been very effective.

HTH

Mad