Event ID 3010 -- Mail not routed to domain on same server

[icartmanxx]

We have an Exchange 5.5 server and have around 8 different email domains all set up as valid inbound email domains using the IMC routing tab. Most users can connect up to our email server and send an email to someone in their same domain, or someone in one of the other 7 domains hosted on our server without any difficulty. Sometimes however users will get a bounced message back stating that the message wasn't sent to the user as the host was unreachable. When I check Event Viewer on the server I see an Event ID 3010 "An attempt to connect to host "domain.com" failed.

Do I need to add these 8 email domains somewhere else in the IMC for the messages to be routed properly?

Any feedback would be appreciated...

Thanks...