Limitation of Exchange Hybrid Centralized Mail Transport

I recently had a curious behavior in my customers Exchange 2010 SP3 hybrid environment with centralized mail transport for Exchange 2010 SP3 Edge servers enabled.

Before I describe the topic in more detail I would like to say thank you to the guys from Microsoft: Timothy Heeney, Scott Landry and Tom Kern helped me with my ‘little’ mail flow problem . Appreciate your help.

My customer is using a smtp gateway for external mail flow as usual. Some of the mailboxes have configured smtp forwarding like ForwardingAddress (mail contact) and ForwardingSMTPAddress (external smtp address directly set on the mailbox).

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