Azure AD Connect prep

Brendan Leddy
Occasional Contributor

Hi folks,


Have a quick question regarding a first time sync of Azure AD Connect.

We're preparing a move to Exchange online, and part of that will be the synchronization of our on-premise AD accounts to Azure AD & 365.


Currently a number of staff in the company already have office 365 accounts (using it for SPOL, SFB and Onedrive), and their current UPNs for logging into these office 365 accounts are actually the same as there NT logins for the on-premises AD directory (e.g.

So when we try and do our initial sync with Azure AD Connect, I'm assuming we'll get numerous sync errors from Azure AD saying that a account already exists with the UPN or alias

My question is, when we do this initial Azure AD Connect sync, is there a way of us instructing Azure AD/365 to merge this new on-premise account with the previously created 365 account of the same name/UPN? Or maybe the initial sync will do this automatically anyway?

Any helpful info on this would be greatly appreciated!!


6 Replies

Thanks Neil,


Unfortunately that link's not working for me, but I'll try and see if I can find the same article.



Right-click it and copy the link, then paste it into a new tab or try this :)

Neil apologies! There was a white space at the end of the URL that i missed.


Thanks again


No worries, did it answer your question?

I think it will work (no sync errors) as long as local UPN matches primary email address in Exchange Online. 

You have to be aware that your local AD will now be the new master data source for all changes to users and groups and other objects. Anyway, it should be more or less safe to play with on test accounts, if you use Group based scoping (default in Express mode) instead of OU based filtering.

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