Email is suddenly being bounced by our Exchange 2003 server, the senders getting the message 'Error 501 - Invalid Domain', and I can see the messages being stopped at our firewall.
The Exch 2003 server co-existed with a 5.5 box for 2 weeks and last weekend the 5.5 box was finally removed from the domain. The 5.5 box was called oldbox and the new one is newbox. A problem with OWA showed that the routing table in our router still showed 'oldbox' - our service provider changed it to 'newbox' yesterday and made sure it pointed to the right internal IP address.
Since then we have had no external email delivered. We can send out no problem. I've run checks on www.dnsreport.com
and it shows everything works right up to it gets to the IP address of our firewall and then it says 'Invalid Domain'. Our external address is outside.org.uk while our internal domain is inside.local.com. Our service provider says the problem isn't down to them, they're delivering the traffic to us, we're not accepting it.
Any help in diagnosing and fixing will be greatly appreciated.