> Regardless, it would > > be nice to see a non-biased, objective comparison of the available > > alternatives. Included in the comparison should be size, > > architectural differences, security features, advantages, > > disadvantages, configurability, customizability, volume capacity, > > memory profiles, system load, etc. Well, I've used both qmail and postfix in a large mail clustering environment, and I'm still using both of them because I did something stupid and added a patch to qmail for functionality not present in postfix, and now the people using the clusters have gotten used to it, so I have to find a suitable workaround to move fully over to postfix. As far as size goes of each system goes, they are probably about the same. Qmail has a whole bunch of config files for different functionality, and postfix only has one main one (main.cf) that you really have to worry about. Qmail runs as a bunch of different users, but all of the processes can still talk to each other. It's probably better from a security standpoint, but postfix runs as non-root also, and you can chroot it if you desire. Both have a process that manages the queue and calls other programs to handle the outgoing mail, and also talks with the smtpd daemon for incoming mail. As far as configurability goes, postfix wins hands down. Like I said before, qmail has config files all over the place, and also requires daemontools to run, which has never worked flawlessly for me. Daemontools adds a little extra setup time to the mix also. Postfix stores all of it's config options in main.cf. You can edit this file by hand, or use the postconf command (postconf -e "option = <your options>"), and then do a "postfix reload" to make them take effect. Very simple, and great for scripting changes across the cluster. Customizability is a toss up. It could be argued that qmail is more customizable because of the enormous amount of patches available for it, but most of these are for functionality that postfix already has. For the most part, you can just enable certain functionality in the config for postfix, qmail will require a patch to the source and a recompile. Most of the time the patches go fine, but if you've done some other patches already, they sometimes don't apply nicely and you either have to do them by hand, or reapply them in a different order. I haven't had to modify postfix at all because it already has all of the functionality I need. System load with postfix is much lower than with qmail. I read a review awhile back which determined that postfix's disk i/o is 1/3 that of qmail. I've seen considerably less disk i/o with postfix on my boxes, and I think this contributes a lot to the reduced load on the system. My qmail boxes choked when they got over 23,000 messages in the queue. I applied the big-todo patch which fixes this to some degree, but they still choked around 45,000 queued messages. There's a tradeoff here with performance too, because with the big-todo patch, it will create a larger directory tree for the queue, which seems to hinder performance. Postfix keeps chugging even with nearly 100,000 messages in the queue. Postfix also supports ESMTP pipelining, which qmail does not. This means that it will open a single connection and send multiple messages destined for that MX over that one connection. It can reduce your overall bandwidth usage by up to 20% because the SMTP setup has a lot of overhead. Qmail only sends one message for a connection, so if it has 1000 messages to send to an MX, it will setup a connection, send a message, disconnect, and do it 999 more times. Postfix will also make parallel connections to speed up delivery, and it will scale back connections if it detects the remote server getting slow. Overall, I see much better performance with postfix, and it's much easier to administer. When I started using qmail 2 years ago, it performed much better so that's why I went with it. But the newer versions of postfix are faster. Qmail hasn't been updated since 1999 and it shows. Jay