I’m involved in a Staged Migration project from Exchange 2007 Sp3 to O365 and I found various problems uploading identites to O365.
My Scenario is:
Forest A with FFL and DFL 2003 with Resources Subdomain with Exchange 2007 SP3 and Users Subdomain where are all user accounts.
Forest B with FFL and DFL 2008 R2 where have a syncro of all users from Subdomain on Forest A.
After I configuring AD Connect and execute users syncronization to Office 365 I saw the following error:
Error: MigrationInvalidTargetAddressException: A valid primary email address email@example.com couldn’t be found on the target.
My problem was that not all user attributes were syncronized from Users subdomain in Forest A to Forest B.
Cheking all attributes I found that I needed the following attributes to syncro from Forest A to Forest B:
Once done, the problem disappeared automatically.
Here you can see all attributes that Exchange Online need from users, contacts and groups.