Send Email without SMTP servers

I am currently working on a POP3/SMTP client. I would like to be able to send email without the use of SMTP servers, or to easily gain access to the user's default SMTP server without them having to enter it in. I know it is possibly, because the trojan subseven allows emails to be sent with specifying a server ## Deliverables All code provided in visual basic 5.0/6.0 Just the code for sending emails with SMTP/or finding local SMTP easily