Over the past 2 or 3 days, I've noticed several IP addresses attempting to carry out “email guessing” attacks. The following IP addresses connect to the mail server I administer, and then send in random names such as joe, john, matt, etc, followed by the domain name I'm administering.

Tough luck! Once I noticed these attacks, I banned the following IP addresses immediately.

List of banned IP addresses

65.96.95.158
66.26.58.168
196.36.0.0 - 196.39.127.255
203.193.133.71
203.199.177.0 - 203.199.177.251
65.216.176.0 - 65.216.179.255
216.146.88.200
155.56.68.170
202.56.230.13
202.54.99.227
130.207.165.165
64.164.98.164
64.164.98.64
65.172.17.116
24.144.4.19
199.185.220.240
67.15.6.3
216.217.139.250
66.195.127.26
203.199.60.115
66.18.69.6
208.54.222.224