Merger Exchange 2000 to a environment of SBS 2003 with a Exchange Enterprise Edition 2003.

Need to merger Exchange 2000 to a Exchange 2003 environment, but I have a small catch.

I have companyA.com that hosts a windows 2000 server with exchange 2000.

Also, I have companyB.com that hosts a SBS 2003 server running CRM 3.0 plus, a server with Windows 2003 Enterprise edition and an Exchange 2003 Enterprise edition.

Now my question is how do I merger the exchange 2000 server (which is companyA’s mail system) to the exchange 2003 server (which is companyB’s mail system)?  I know it would be easy to do this using AD, but since SBS 2003 is in the picture I know that you can’t have domains trust each other.

Does anyone know of some kind of work around?

My only guess is that I manually change the recipient policy of companyB.com to include companyA.com’s domain.  Then create mailboxes on companyB’s exchange server 2003 that have the same naming conventions of companyA’s exchange 2000 server and then finally change the publicly hosted MX record for companyA.com to point to companyB’s publicly hosted MX record.

Or does anyone else have a better suggestion to the problem?
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