I ran across another problem. When accessing an account with a very large number of emails, sometimes YPOPs doesn't return a line with a ".\r\n" at the end of the message, when doing something like "RETR 2". This causes most mail clients to wait forever for the rest of the message. Again I wrote my own pop3 client, and my solution was to sleep (to wait for data to arrive), and then try to do a non-blocking recv on the socket. If there is data to read I keep going, once there is no more data I know that the message is done, whether or not there is a line with a dot. However I don't understand at all, why YPOPs is not sending the line with the dot at the end.