Sunday, July 7, 2002 08:04 PM
Email exchange _always_ takes place on port 25, regardless of how you actually interact with the mail server. Port 80 is only used between your web browser and a web-based email client, not for the actual transfer of emails between servers. Hence, if you use MS Outlook, outgoing emails will be sent using SMTP on port 25.
This is all documented in RFC821 and RFC822.