I’ve been running Postfix on all my servers for many years now. Postfix has proven to be fast, stable, and reliable.
I’ve had some complaints, though. The main one is its filtering support. It doesn’t support filtering during the SMTP transaction. (Well, OK, recent versions do, but not very well.)
The other problem with filtering is that all of the plug-in filtering solutions stink. I am using Amavis, which is the best of them, but it still uses about 40MB of RAM for each new message, and is rather unstable.
So, I’m trying out Exim. It appears to be much more configurable than just about anything, though its queue manager is not as powerful as Postfix’s. From what I’ve read, Exim has the same peak throughput as Postfix, but a gentler ramp-up curve. That’s fine with me.
For me, the killer app for Exim is exiscan-acl. Spam and virus checking at SMTP conversation time, and a RAM overhead of about 1/80th of Amavis.
I found the Spam Filtering for Mail Exchangers HOWTO to be quite helpful. There is also an exiscan tutorial out there.
So far, I’m really liking it, though I’m having a small problem on my Alpha.
That’s quite cool. I’ve been thinking of looking into filtering at SMTP transaction too. I’d love to be able to severely throttle a spammers mail server by taking a LOOOOONG time to respond during the SMTP conversation. If everyone did it, it would drag their machines down so bad, it would be like enforcing a “time price” for each spam sent (though this does nothing for hijacked/relayed hosts).
Just be damn sure you don’t catch *non-spammers* with that crap. Busy mail servers aren’t likely to be interested in sitting around waiting for you to respond to a MAIL command because you think it hurts spammers. Instead they’ll drop the connection and move on and let your mail get dropped into the ‘slow’ queue for delivery hours later.
Indeed, good point. As much as I like email though, I still consider it a “best case scenario” these days, so I’m fine if good emails never get to me. That’s why I have a phone/cell phone, instant verifiable communication. :-)
A couple of days ago, I wrote about considering a move from Postfix to Exim. I have just made that move on the main server. It took about three hours and was successful. Here’s what I learned.
My fears about Exim’s queue management being less s…