NDRs to external recipients in same company domain Exchange 2010

Just migrated from Exchange 2003 to 2010 (SBS) and all is well on the email front except when sending emails to people who are on the same company domain (ie user@mycompany.com) but work in a different office so are NOT on the Exchange server (so to all intents & purposes they are external recipients), all mail bounces with:
"The email address that you entered couldn't be found. Check the address and try re-sending the message. If the problem continues , please contact your helpdesk".
Most search-engine hits point to issue with auto-complete / address list within Outlook with solution of deleting all auto-complete entries and typing in full email address. But discounted this by not only trying it from different machines but by sending the emails from internal webmail (ie https://mySBSserver/owa) where there IS no auto-complete and get identical NDRs. So 95% certain it's a server issue not an Outlook issue.
In Exchange 2003 in a case where you had recipients located outwith the Exchange organisation but with the same company domain name, you always had to specify an smtp setting under "Default SMTP Virtual Server/ Messages /Forward all mail with unresolved recipients to host" as otherwise Exchange will look for the recipient in its own user list, not find them and give up. I'm sure this is where my issue lies but not seeing an equivalent setting in Exchange 2010. Inclined to think I need to be messing with the domain setup in Org Config / Hub Transport / Accepted Domains but struggling to figure what to do in here, if it is here I need to be.
laurencoullAsked:
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Alan HardistyCo-OwnerCommented:
There is a nice walk through detailed in the following blog:

http://telnet25.wordpress.com/2010/08/08/internal-relay-domain-forward-all-mail-with-unresolved-recipients-to-host/

Basically you have to convert your default Accepted Domain to an Internal Relay domain and setup a SEND Connector scoped to send to a Smarthost (the external server handling the other email addresses not on your server) and job done.

Alan
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Cris HannaCommented:
Alan has provided the 'new method' needed for this new version of exchange, but I would suggest that there is an even better option.  
I'm betting that on the SBS server you're using the POP3 connector?  Why not have all email come straight to the SBS server and have the remote users connect to the SBS server using Outlook Anywhere?
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laurencoullAuthor Commented:
Great article, thanks!
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