Postfix – rejects non-existing accounts
One of the biggest differences between Postfix and qmail is that Postfix comes out of the box (more readily) configured for anti-spam functionality. A big feature (for us) is that Postfix will immediately reject messages targeted at accounts that do not exist. It appears to immediately disconnect and short circuit the connection.
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Goodbye to qmail
We have been a qmail shop since 1997 and I for one am fed up with qmail. Good god it’s been stuck at 1.03 since I started using it and now has a myriad of patches. It can only be installed from source, and there are quite a few sources required. I had difficulty getting the patches I wanted to work. Support has always been poor and documentation weak (except for the excellent http://www.lifewithqmail.org/). When we began rebuilding our unix platform from the bottom up we decided to bail on our old friend qmail.
One interesting thing: In the last year or so we began to be targeted with massive amounts of spam being sent to nonexisitant accounts at all of our domains (we have about 10). My haunch is that the spammers were actually counting on the bounces that our server produced to send spam. I tried a few times to configure the validrcptto patch to stop this but was unable to get it to work. The amount of bounces went from almost zero to hundreds or thousands a day.
Good riddence to qmail!