hello there.... i believe that this is not a supported configuration in Exchange 2010, but would like some confirmation. As far as I am aware this isnt possible. The idea is as follows....Post merger, the environment consists of a POSTFIX server on SITE A and an Exchange 2010 org on SITE b. The POSTFIX is being configured to recieve all email addressed to company.com. local users on SITE A will POP their email directly from POSTFIX server. the intention then is to get the exchange 2010 to POP SITE B users email to the relevant exchange mailboxes. SITE A and SITE B will send email outwards from their own internet connections. Stephane Fa

If there is a always-on connection between Site A and Site B I'd suggest a SMTP Name Space Sharing scenario, where Exchange/POSTFIX sends email for unresolved @domain.com receipients to the other email system. I have no idea how to do this in POSTFIX but in Exchange 2010 you do as follows: Configure Exchange 2010 to Route Messages for a Shared Address Space Please also remember that if you allow both sites to send outgoing email in the name of @domain.com you proberbly would like to update the SPF record to allow all the external sending IPs to send in the name of @domain.com. Here's a great resource: Sender ID Framework SPF Record WizardJesper Bernle | Blog: http://xchangeserver.wordpress.com

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