We are in the process of migrating from O365-> On-Premise.
Currently, the email domain hosted by O365 = domainA.com
We have built an AD infrastructure with the dns name of AD.domainA.com
2013 Servers have been built. Exchange is currently working with the test email domain domainB.com flawlessly.
This is a greenfield Windows AD deployment. I've joined a workstation to the new domain. workstation.ad.domainA.com
I have a user John who has an active mailbox on O365. His mailbox also has full access permissions for 3 other shared mailboxes.
if i login to the domain, and add his O365 account, Outlook will add his mailbox, but keeps prompting for his password. It will also prompt for the password to the shared mailboxes.
It will accept the password to his mailbox eventually, but it will not accept it for the shared mailboxes (its odd its even being prompted for this isn't it?) If i click OTHER USER in the prompt, and manually enter his O365 credentials, it still does not work.
Now, if i add his O365 account to my personal Outlook from my office (not connected to their domain) everything seems to work fine.
I suspect my having named our AD domain with a similar root ad.domainA.com is creating some sort of hiccup in authentication. I've considered renaming my domain, but just read I cannot do this as it will break Exchange 2013.
Do I have any recourse? One option would be just to wait until the O365 cutover time to join their computers to the domain, but there are a bunch of machines, and i'd rather get them joined and their profile data moved over ahead of time.
Any help would be greatly appreciated.