Pop3 Timeout problems

[Jose]

Lately, my server has been having problems with POP3 timeouts.

Using Qmail 1.03 and the pop3 daemon that comes with QMail.

I'm getting many calls from clients claiming that their email programs
say: POP3 Server not responding, etc.

This occurs during an email download.  Some will be halfway through, or
1/4 or 90%.

What is causing these pop3 timeouts?

Thanks,

Jose de Leon