I have an article titled debugging SSL in the December issue of SysAdmin magazine. The article covers techniques to debug SSL communications, and includes several useful examples. One of the examples shows how openssl can be used to check the operational status of a POP3s server. This is accomplished by feeding POP3 commands to openssl ( or telnet if you want eavesdroppers to learn your username and password ):
$ openssl s_client -connect prefetch.net:995
CONNECTED(00000003)
[ ... ]
user ME@my.domain < ---- This is the username you login as ---->
+OK Name is a valid mailbox
pass SOMETHING_OR_ANOTHER < ---- This is your POP3 password ---->
+OK Mailbox locked and ready
list
+OK scan listing follows
1 1518
retr 1
+OK Message follows
dele 1
+OK message deleted
quit
+OK
This allows you to open an SSL connection to your mail server, “list” the messages in your inbox, “retr” message number 1, and “dele” it after you are done reviewing it’s contents. This also has the awesome feature of dumping the complete headers from the message (most email clients provide this capability as well). The headers can help you get an idea of which path a message took to get to you (when the headers have not been modified).