[1]My Application needs to send Mail [No need to receive mail], Is There any way to send mail using only POP3 Authentication [Not using SMTP Authentication]

[2]What is the difference between POP3 and POP Before SMTP

I'm trying in 2003 Exchange Server, language VC++ or C Sharp
Thanks in Advance

POP3 is only to receive, SMTP to send. If you need to send mail, you have to do so through some mail server somewhere, and that server will require authentication of some sort.

Just open any mail program and you can see how to set up authentication. Either SMTP uses the same user/pass as POP3, or you send an individual user/pass. On most setups, POP3 will be whoever you get mail with (gmail etc. al.), while SMTP will usually be your ISP, that is your local cable company or DSL provider.

I know you're doing this in Exchange and CS but the idea is the same, your SMTP authentication is probably through your ISP because they may not allow email to transfer through their servers.