I just inherited a exchange 2003 SP2 machine and next month we are migrating to 365. But here is what happen so far and the issue
1. The previous IT company had the emails flowing thru smart host via their own hosted spam filter.
2. I came in and changed my MX records and installed a on server spam filter (ORF) by Vamsoft and configured it. Removed the smart host info and made sure that the firewall is all configured properly.
3. Tested in bound email.
4. Problem. Out bound emails go thru till the server. Some users get a delayed email but others do not. The messages are stuck in the outbound Queue. restarted the SMTP and still no luck. Disabled Spam filter (ORF) still no luck.
Then I looked at anything which is common.
mails to msn.com & Hotmail.com are stuck. Emails to my company tejes.com are stuck. There are other few companies but do not know their email provider but the common theme between these 3 domains all are hosted by Microsoft. tejes.com is on office365.