[Tip courtesy of Emil from Algorithmics via our Forums.]
Symptom: Sending SMTP e-mail from any POP e-mail program (Outlook 2K, Outlook Express, Eudora) causes a delay of 30-60 seconds before a connection is made to the SMTP server to send mail. Sometimes the email program times out waiting to connect to SMTP server. Sending attachments is painfully slow. Bypassing the router and connecting the client computer directly to the Internet results in normal mail sending speed.
Solution: Your SMTP server could be trying to use the IDENT protocol (also known as IDENTD) to authenticate you. Try forwarding Port 113 (TCP if you need to specify it) through your firewall to the IP address of the computer that is trying to send email.