We're in the process of migrating users and systems from domain1.com to domain2.com. Our Exchange 2013 is in domain1.com. We're hoping to find a way to move some users and systems into domain2.com and still have them get their mail from domain1.com until someday when we move Exchange over to domain2.com. Is this possible to configure so Auto Discovery configures users in domain2.com with Exchange in

Yes, it's called a linked mailbox.

https://technet.microsoft.com/en-us/library/jj673532%28v=exchg.150%29.aspx?f=255&MSPPError=-2147217396

Ah...you're a genius Ed. Thanks for the information!

You're welcome.  Happy to have helped.