Exchange 2010 conversion from Hyper-V to ESXi

Hi!

I have a frustrating problem.

I have an Exchange 2010 running on Hyper-V flawlessly.
We are about to migrate from Hyper-V to VMware ESX (5.x).

For this purpose I have stopped the Exchange services on the Hyper-V and used VMware converter to create a VMware image. I have stopped the LAN card on the Hyper-V version and started up the VMware version with the same IP as the old one.

Everything seems ok, services start, databases mount etc, but I can't send to our domain from external mail addresses. So if I send from a gmail address to my internal mail address I receive "Unable to relay". I have checked if the domain is added in the config etc, that's no problem.

I tought it was related to the VMware converter so I tried the whole thing with Acronis Backup and Restore (long run), but the problem is the same.

I have no idea what I am doing wrong and what could possible cause the problem above. The new image should be identical to the Hyper-V version.

Can you guys give me some hints?

Thanks,
Daniel