Originally posted by: SystemAdmin
The use of a smart relay may be the easiest option. However, if DNS is setup at your location then it is not necessary. Try:
nslookup -querytype=MX your_domain.com
and look for lines containing information about the mail exchanger. My guess is that the DNS server(s) at your location do not know about the Exchange server, so you need to use the smart relay.
If your Windows systems use the same login name as the UNIX systems, then you should be able to send mail from the UNIX hosts. However, we had trouble sending e-mails outside of the company with Exchange. It turned out that we had to use the Windows e-mail name as the Sender, or the mail was blocked by the Exchange server.