I have recently migrated from exchange 2003 to 2010. Both exchange servers have been working fine, internal and external mail.
We have our roter managed by external services. I have had to have the mail IP changed from the old mail server to the new one.
At the same time I also decomissioned the 2003 server in the correct way according to ms documentation.
After this I can not receive external mail to the 2010 server.
I can send out mail, I can send and receive internally mail OK but no external mail is getting in.
I have run some tests
canyouseeme.org shows port 25 is open and it appears it is pointing to the correct IP.
I have run the exchange 2010 SMTP check mail and this shows all green ticks.
Any suggestions how I can troubleshoot this further?