Hi,
We are currently in the process of migrating from Exchange 2003 forest A to a Exchange 2010 forest B. That needs a shared smtp (@test.com) for the co-exsistence period for the migration. All outside email flows from to Exchange 2003 which then relay emails to Exchange 2010 (via SMTP Connector). A two way forest trust is setup, DNS with conditional forwarding between the two forests, I have set Exchange 2010 as Authrotative (for @test.com) and Exchange 2003 as non-authorative (I have setup a dummy smtp domain @test.local as the authoraitive domain in the email receipt policy, and set @test.com as non authorative). And is using FIM 2010 to sync mail enabled contacts from Exchange 2003 forest to the Exchange 2010 Forest and vice versa with @test.com as the SMTP address.
Mail flow works for a short period before NDR gets generated. Or inbound email (outside to Exchange 2003) stops working completely. Is there a mail loop occuring or NDR loop i am not aware of?
(e.g. A configuration error in the e-mail system caused the message to bounce between two servers or to be forwarded between two recipients. Contact your administrator.<#5.4.6>)
I am also aware that I can change the contact smtp to user @test.local, but this will be a issue when users reply to a email with internal/external reciepts. (e.g. bob@test.com reply email to jane@test.local and joe@gmail.com, when joe replys the test.local will cause a NDR.
Please advise, sorry for the long post, just wanted to be detailed.
