Postfix and Spamassassin - only scan incoming mail
Hey all, this is my first post here, I hope you can help me!
So basically, my problem is this:
I have a mail server, (well, actually a server that does it all: DNS, mail, apache, etc) and i've noticed that spamassassin scans all email (incoming, outgoing - even from our own users). Now, this really isn't a problem, the CPU usage is rather low, but it's been bothering me ever since. So, the solution I came up with was to tell postfix to "content filter" only mail coming through eth0 - the external interface; mail coming from the local network and localhost (for mail sent from squirrelmail) won't be sent to spamd for checking.
Well, this works... in some cases, but it's really not a viable solution since:
a) a lot of our users have notebooks and have wireless connections, so they connect to the server on the public IP
b) even if they are connected to the local network, their smtp server in the mail client is the mail subdomain itself, so the connection, again, will be established through the external interface. I'd have to set every mail client in the company with the internal IP of the mail server... so it would be a real drag.
The solution I think would work best, would be to somehow tell postfix to only send spamassassin mail which isn't sent by one of our users (the mail users being actual linux accounts). Does anybody have a clue how on earth could I accomplish this?