Is Exchange delivering the mail to Wingate OK?
Exchange works better with Wingate, if you set up an SMTP connector with Wingate set up as the Smart host.
http://support.microsoft.com/default.as ... -us;265293
Or, is it Wingate that cannot deliver the mail?
If this is the case, there could be any one or more of serveral problems, depending on the SMTP server Wingate is trying to deliver to.
1. Your IP address could be on a black list.
2. Your ISP has blocked port 25 to SMTP servers outside of its relm from its client IPs, if this is the case see if your ISP will unblock port 25, or use your ISP's SMTP server as a relay.
3. You may not have a PTR record for your public IP Wingate delivers mail on. (Many if not most SMTP servers require PTRs for SMTP servers delivering to them.)
These are the major reasons most mail servers would not accept mail from yours. There are many other problems that are only supported by some SNTP servers, SPF, EHLO/HELO greeting, MX lookup or many other reasons. The only way to tell for sure is through testing you mail domain.