I've brought our new Exchange server online and outbound mail is fine.
Telnet on port 25 is fine and our mail host can successfully send in, but only by using email_address@domain_name.domain_name.com
So, somehow, somewhere, I have a problem where our domain name is listed twice.
Having sent out test messaged I can also see that the message header contains this same reference.
I've also tested it from a remote location and had a "No valid recipient" and "unable to relay for..." message, when using our standard email_address@domain_name.com addresses.
Where do I look, and how can I fix it ?
This is urgent, and I'm starting to get a bit twitchy about it.
Any and all help VERY gratefully received.