I have a SBS 2003 R2 server that is running Exchange and is attached the Internet via a dedicated IP cable modem in the New York area. The ISP is Road Runner. I am having a strange problem where e-mails sent from this server to a certain other ISP (ptd.net) will never make it to their destination e-mail boxes at ptd. They do not bounce nor do we receive any warning messages. I have tested sending to many other domains and it works fine. The server also receives e-mail fine, even from ptd.net. I confirmed with ptd that we were not in the black list at ptd.
Anyone have any ideas??