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I'm in the process of moving a client from internal Exchange 2007 to hosted Exchange 2007. However I have a requirement Where I have to move half the client's employees one week, and half the next week. In the meantime, they still need to be able to email each other.

Is it possible to create a transport rule so that when email is sent internally, it is also routed to the hosted Exchange server? What might that transport rule look like?

I have full admin access to both internal and hosted Exchange.

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up vote 3 down vote accepted

You're basically talking about the on-site Exchange server no longer being "authoritative" for your Customer's domain (since there will be another SMTP server where other recipients in that domain exist at the hosting provider).

A transport rule isn't going to do what you want, but there's other built-in functionality that will.

You need to configure the Customer's domain as an Internal Relay domain in their existing Exchange organization. This tells Exchange that it's not authoritative for the domain and causes it to deliver any messages that have unresolved recipients in that domain (which gets those messages delivered to the hosting provider (for the already-migrated users). Your hosting provider Exchange organization is going to need the same configuration so the already-migrated users can send messages to the yet-to-be-migrated users.

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Awesome, this is exactly what I needed, thanks! Any idea if I can convert an existing authoritative domain into an internal relay domain? The authoritative domain is the one that was specified when Exchange 2007 was installed. Hub transport/mailbox store roles are all on one server. – DomoDomo Nov 27 '11 at 22:07
I just looked at the GUI for this in Exchange 2007. Looks very straight forward. There's simply a radio button where you can select 'Authoritative Domain', 'Internal Relay Domain', or 'External Relay Domain'. Easy enough. – DomoDomo Nov 27 '11 at 22:16
Yep cool I just set this all up by switching the Authoritative Domain to an Internal Relay Domain, then adding a new send connector for just this domain, and was able to route between the old internal Exchange 2007 server and Hosted Exchange 2007 server perfectly. Thanks again. – DomoDomo Nov 27 '11 at 22:41
Glad I could help. – Evan Anderson Nov 28 '11 at 0:34

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