Set up AD sync for Exchange 2010 hybrid - UserPrincipalName match e-mail?

I am looking to get going on setting up an Exchange 2010 hybrid for my existing on-premise Exchange 2010 server.
From what I understand, the first step in this process is to setup a new server for Active Directory synchronization with O365, is that correct? Should it be its own server or should I install that on the Exchange 2010 server?

As for the AD sync step, should I configure everyone's AD account UserPrincipalName to match their E-mail address? The reason I ask is because in our forest, there are two domains and potentially duplicate usernames/samaccountnames.
So my understanding about the AD sync is that it might be better to ensure everyone's UPN is unique before starting the sync, and ensuring everyone can login to Exchange Online with their UPN federated domain instead of local.domain\username.
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Will SzymkowskiSenior Solution ArchitectCommented:
I would highly recommend that you take a look at the Exchange Deployment Assistant as it will outline all of the necessary steps based on the type of configuration you want to deploy.

This will provide specific steps for Exchange 2010 Hybrid setup and how to get there. Just answer a few questions and it will then provide you with all of the necessary steps.

Exchange Deployment Assistant


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Vasil Michev (MVP)Commented:
It's not necessarily for the UPN to match the primary SMTP, but it will save you some trouble. Also, federation is NOT required for Hybrid, and is different from dirsync. Review the documentation as Will suggested above to familiarize yourself with the key points.
garryshapeAuthor Commented:
I'm going through the deployment assistant I'm just not sure it's going to advise thoroughly enough on handling duplicate usernames
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