While qmail is generally fast at processing, routing, and delivering email, in some circumstances its speed can be improved. This involves either tailoring qmail to take full advantage of the available hardware or improving the hardware. The best strategy depends on the situation.
It is important to first determine what speed is theoretically possible before analyzing qmail to find problems and improve speed. Qmail's ability to deliver email quickly is limited by several physical realities, including:
Network bandwidth
Disk-drive bandwidth
Server memory
For example, if an email server is connected to the Internet by a 320kbps link (or 40 kilobytes per second) and if the average email is ten kilobytes, then only 4 emails can be transmitted per second. That means 240 messages per minute, and 14,400 messages per hour, as long as there are no other forms of traffic on the network and (inaccurately) assuming there is no SMTP-protocol overhead. Thus, delivering...