Have you been struggling to send email from BizTalk 2004? Have you ever seen the message:
The adapter failed on an attempt to transmit a message going to send port with the address "mailto:xxx". Details: "Finding document specification by name failed. Verify that the schema is deployed properly."
If so, you probably haven't configured your SMTP send adapter. See Steps 7-9 on this MSDN page on how to do this. Personally I'd have picked that error message to say "Your SMTP adapter is not configured" but that's just me ;-)