Why is it called Mail Toaster?
A toaster, by definition is a device for toasting bread. A long time ago (in computing terms) a computer arrived on the scene which was good for only one commercial purpose. The computer was the Amiga, and combined with a special card, it was known as the Video Toaster and it did video like nothing else. Video could have been its killer app but the company didn't survive.
Years later, devices came and went, but on occasion, a system would come along that was designed for only one purpose, such as the Cobalt Cube. In computing circles, such devices would be known as web toasters. You plug them in, use them for their one purpose, and that was that.
Devices like the Netapp Filer come to mind. At internet trade shows such as BBSCON and ISPCON, it was common to refer to them as file toasters. The name stuck. You would buy one, plug it into the network, and use it for its intended purpose. It is this definition of toaster that we are using:
toaster: n. - A specialized computer used like an appliance.
The Mail::Toaster is designed to take whatever PC hardware you have and turn it into an email server. It can and has been used in many other ways since. It is not required that you use it strictly as an email server, but that is the assumption. Mail::Toaster was born in a data center, on two racks full of computers all built to function together as one big email server. Its naming is a function of that heritage.
The photo is Mail::Toaster 1.0. At this scale the system was serving approximately 20,000 email accounts. The hardware is quite meager by modern standards. The 4U systems are Micron 3400's, some of the worst hardware I've had the privilege of using. The specs vary between uni and dual proc PIII 400-550 MHz. On the right side is (starting from the top) an ATA RAID array, a 6U Micron Quad Xeon 550, and two more 3400s. Those three were the MySQL replication masters as well as file servers.