I use fetchmail as an IMAP client to check/retrieve my richard.perry@villanova.edu email every 30 minutes. Since fetchmail logs connection failures, and I have logs going back about 8 weeks, I can produce some statistics about the uptime of the Villanova po.villanova.edu email server.
For example, from 28 July 2002 to 23 September 2002, an interval of 58 days, my fetchmail IMAP connections failed 43 times. That is an average uptime or reliability of about 98.5%. That doesn't seem too bad, it is an average downtime of about 20 minutes per day. On the other hand, it may seem really bad if you needed access to email when po.villanova.edu was down, because the outages tended to happen over consecutive hours of time, like all morning September 18 from about 07:04 to 12:34, and September 21 from about 07:34 to 10:04.