The easiest way to change mailbox to different domain user

Hi guys.

1 Forest with 1 Exchange organization.

2 domains and each domain has exchange installed on their side.

We have a situation where domain user is located in domain1 but his mailbox is located on exchange server in domain2.

Now this user geographically moved to location of domain2 and now he has domain user created in domain2.

The idea is that we would link his previous mailbox to this newly created domain user, so he would keep the same mailbox (he would like to keep it, because of bunch of subfolders, outlook rules etc)

Possible?

With best regards 

bostjanc