qmail's modular, lightweight design and sensible queue management make it the fastest available message transfer agent. Here's how it stacks up against the competition in five different speed measurements. * Scheduling: I sent a message to 8192 ``trash'' recipients on my home machine. All the deliveries were done in a mere 78 seconds---a rate of over 9 MILLION deliveries a day! Compare this to the speed advertised for Zmailer's scheduling: 1.1 million deliveries a day on a SparcStation-10/50. (My home machine is a 16MB Pentium-100 under BSD/OS, with the default qmail configuration. qmail's logs were piped through accustamp and written to disk as usual.) * Local mailing lists: When qmail is delivering a message to a mailbox, it physically writes the message to disk before it announces success--- that way, mail doesn't get lost if the power goes out. I tried sending a message to 1024 local mailboxes on the same disk on my home machine; all the deliveries were done in 25.5 seconds. That's more than 3.4 MILLION deliveries a day! Sending 1024 copies to a _single_ mailbox was just as fast. Compare these figures to Zmailer's advertised rate for throwing recipients away without even delivering the message---only 0.48 million per day on the SparcStation. * Mailing lists with remote recipients: qmail uses the same delivery strategy that makes LSOFT's LSMTP so fast for outgoing mailing lists--- you choose how many parallel SMTP connections you want to run, and qmail runs exactly that many. Of course, performance varies depending on how far away your recipients are. The advantage of qmail over other packages is its smallness: for example, one Linux user is running 60 simultaneous connections, without swapping, on a machine with just 16MB of memory! * Separate local messages: What LSOFT doesn't tell you about LSMTP is how many _separate_ messages it can handle in a day. Does it get bogged down as the queue fills up? On my home machine, I disabled qmail's deliveries and then sent 5000 separate messages to one recipient. The messages were all safely written to the queue disk in 23 minutes, with no slowdown as the queue filled up. After I reenabled deliveries, all the messages were delivered to the recipient's mailbox in under 12 minutes. End-to-end rate: more than 200000 individual messages a day! * Overall performance: What really matters is how well qmail performs with your mail load. Red Hat Software found one day that their mail hub, a 48MB Pentium running sendmail 8.7, was running out of steam at 70000 messages a day. They shifted the load to qmail---on a _smaller_ machine, a 16MB 486/66---and now they're doing fine.