The comparative performance study covers the four basic functions of electronic messaging: message receiving, their delivery to the user’s mailboxes, message storage and user accessing stored emails. Two usage scenarios were considered: business and ISP. The tests consisted in sending messages with a predetermined size to the servers and checking their acceptance in the users’ mailboxes.

The large number of spam messages from the total traffic of received email messages (estimated by Radicati, in 2007, at 72% of all traffic) generates frequent periods of intensive server usage. To verify the servers’ ability to respond in overload conditions, their response time to requests on 1, 2, 4 and 8 parallel connections was tested.