I work at a medium sized ISP, and I have a qmail running on FreeBSD for about 6000 users.
I use mysql for storing and validating the usernames & passwords, and the mailboxes are on our main (raid) file server mounted by nfs, over a 100mb ethernet. It would be pretty straightforward to add more boxes to cope with higher load, I would probably just need some kind of round-robin dns to spread the load accross the boxes.
I wrote the mysql hacks myself, by rewriting the checkpassword program (for pop3) and the qmail-local (local delivery agent). This makes it possible to use a web interface to add/remove mail boxes, and to integrate it with our billing software. I've used perl scripts to do it, although it is showing to be a bottleneck, for any larger demands it would be best to do it in c.
The stability and reliability is excellent, for example after having a (long) network outage, we recieved 60,000 messages from our external backup mail servers, in a burst. It took a long time to deliver them (probably because of my perl scripts:-), but they were queued up, and all successfully delivered.
Slashdot Mirror
I work at a medium sized ISP, and I have a qmail running on FreeBSD for about 6000 users.
:-), but they were queued up, and all successfully delivered.
I use mysql for storing and validating the usernames & passwords, and the mailboxes are on our main (raid) file server mounted by nfs, over a 100mb ethernet. It would be pretty straightforward to add more boxes to cope with higher load, I would probably just need some kind of round-robin dns to spread the load accross the boxes.
I wrote the mysql hacks myself, by rewriting the checkpassword program (for pop3) and the qmail-local (local delivery agent). This makes it possible to use a web interface to add/remove mail boxes, and to integrate it with our billing software. I've used perl scripts to do it, although it is showing to be a bottleneck, for any larger demands it would be best to do it in c.
The stability and reliability is excellent, for example after having a (long) network outage, we recieved 60,000 messages from our external backup mail servers, in a burst. It took a long time to deliver them (probably because of my perl scripts
Overall, I would strongly recommend qmail.