>> You can use IMAP as a means to authenticate a user before he (or
>> really, his/her IP address), is allowed to relay mail via SMTP.

> could you point me to some URL about it?
> especially dumb-guide for windows user how to configure outlook.

You shouldn't really need to configure outlook any more than normal,
the only thing you need to do is make sure that you always check your
mail before you try to send any, so the IMAP authentication happens
before the SMTP. The following is probably a good starting point to
read (from pkgsrc/mail/drac/Makefile):

    http://mail.cc.umanitoba.ca/drac/

Regards,

        -- Urban