Have company A.com (80 mailboxes) and they bought company g.com (540 mailboxes).
a.com has a local AD forest a.local (2012) that uses Azure ad connect to sync with an O365 instance.
G.com has an on-premise AD forest g.corp (2008 R2) and on-premise Exchange 2010 sp3 running Mailbox, Hub, and CA rolls.
(no edge server)
A.com came up with ag.com domain name to represent the new company and added as an alias to the o365 a.com domain .
The execs of A.com want this merger of email done like last week. :)
Trying to put together an approach that makes sense. New instance(move both) , merge into existing instance.... etc..
Has anyone done this type of mail merge?
Trying to see if ag.com needs to be a new instance that we migrate everything to or would a hybrid approach with current a.com and leave ag.com and g.com as alias.