How to send Email without using MS Outlook?

Hi,

I have a code for send/receive email using MS Outlook
but the problem is some of my clients are not using MS Outlook so I can't use that code.

I try to use CDO's and VBSendMail.
CDO's - > It is very difficult to find the port and smpt mail for all the domains[paran,nate,daumn,naver,gmail,yahoo....]
VBsendmail - It's not working in windows7.

So could you give some idea to send mail with all domains?

thanks in advance,
thenndral