>Hotmail and MSN accounts are accessed through HTTP and WebDAV protocols -- Web Distributed Authoring and Versioning. Quite different from SMTP protocol.

You said: "Unless you send email from Hotmail or MSN account"

Where are you sending the email to? We aren't discussing how the email is accessed (HTTP vs. POP).

< update >
Are you saying that it doesn't involve SMTP if you send an email from one hotmail account to another hotmail account? I'll buy that. Also, if one user on a given Exchange server sends an email to another user on the same Exchange server, it might not use SMTP either....