well, despite your skills a smtp client (although minimal) is not the easiest thing of the world.
anyway the only resources you need to watch are:
- handling of the sockets (obviously)
- smtp rfc
http://www.ietf.org/rfc/rfc2821.txt- remember that the smtp server to contact is not your but the one of the destination mail retrieved through the MX dns record
if you want to avoid all these troubles search on internet a free smtp library which does the job, it could be suggested in this case