We are in the process of transitioning from an internally based Exchange system to Exchange Online. My organization consists of two different companies, each with their own domain. The hatfield.com domain was the first to move to Exchange Online and it went smoothly. When I initially signed up for Exchange Online it created a domain of @hatfield.onmicrosoft.com, then I also created @hatfield.com to reflect the email addresses we had already been using.
The problem started when I tried to do a directory synchronization of mccoy.com. I created and verified that domain successfully. However, the directory synchronization is not working correctly. Rather than creating JDoe@mccoy.com in Exchange Online it created JDoe7925@hatfield.onmicrosoft.com.
I have contacted Microsoft Support, and they are still trying to figure it out. Has anyone else seen anything like this before? Does anyone have any ideas how to resolve this issue?