Set a customized sender email address

[Johannah]

I want to use MSN mail to send emails, while showing a different sender
address than my MSN email so that I can use my domain name as an email
address. (My DNS server automatically forwards emails sent to my domain name
email address to my MSN account.) I could do this just fine with a POP3
server by entering the email address of my choosing when I set up the email
account in outlook. But, when I switched to MSN, with an http server, it
doesn't seem to allow me to show any email address except my MSN address when
sending.