Using postfix to relay to MS Exchange allowing only mail to my domain

rsduhamel · 05-13-2011, 01:50 PM

I'm using Ubuntu Server 10.04 and I can successfully relay mail generated by php scripts through an Exchange server.

What I want to do is accept incoming mail from the Internet through postfix and relay it to the Exchange server but I want all mail that is not addressed to ...@mydomain.edu to be discarded.

tva · 05-13-2011, 02:51 PM

Well, you only need to relay .@mydomain.edu to your exchange so other domains remain for postfix to decide whether discard or what to do to them.

So basically you need

entry in /etc/postfix/transport

Code:

mydomain.edu smtp:ip.address.of.your.exchange.server

entry in /etc/postfix/main.cf

Code:

transport_maps = hash:/etc/postfix/transport

I also have

Code:

relay_domains = $mydestination, hash:/etc/postfix/relay

And in /etc/postfix/relay I have

Code:

mydomain.edu OK

Then you need to

Code:

postmap /etc/postfix/transport
postmap /etc/postfix/relay

and reload postfix.

rsduhamel · 05-13-2011, 05:34 PM

Thanks for the quick reply. I'll try that ASAP.

My goal is to prevent Exchange from being an open relay. Yes, I know that you can configure Exchange not to be an open relay but my server doesn't seem to get the message (got blacklisted once already). I don't want postfix to be an open relay either. I would just as soon have it dump any mail not to my domain. Any further advice, if necessary, would be greatly appreciated. Thanks.

tva · 05-13-2011, 11:24 PM

If exchange isn't getting mail from other sources than your postfix you should add postfix-servers ip to allowed sender ip's and deny all others on that machine. Can't really remember exact place from top of my head, somewhere in SMTP connector IIRC. Might depend on exchange version, but I could look that up if you need help on that and tell me your server version. (2003/2007/2010)