Changing SMTP of dirsync user in O365 who has no onpremise account

We are using a hybrid migration and have some users in AD who don't have an on-premise email, but who will once we move them online. How can we set their primary smtp address on O365 ?

From experience when I try and change an attribute of a synced user it looks for us to change on-premise.

Will it just allow me to add a Primary SMTP since it doesn't have a on-premise account ?
Confused as to whether I need to create an on premise mailbox just to change primary smtp ???
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Cliff GaliherCommented:
In an Exchange hybrid topology, all account management is done on-prem.  When properly configured, the Exchange tools (such as the EMC in Exchange 2010) will "see" mailboxes that are in the cloud, not just the ones on-prem.  So you don't need to create an on-premises mailbox, but you *do* need to edit the properties via the Exchange tools for the account.

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Vasil Michev (MVP)Commented:
Just to add, there is one exception to the above - you can 'overwrite' the primary SMTP address of a cloud mailbox via the following cmdlet:

Set-Mailbox -WindowsEmailAddress

Open in new window

This will set as the primary SMTP address for the mailbox, while preserving as secondary. But you should only use this workaround when there is some reason for not being able to change the address on-prem, as Cliff explained.
paologiorgioAuthor Commented:
Cheers Guys,

Cliff , when you say edit the exchange tools, I wonder does editing the Proxy Address of the AD account cover this,
does editing the General Tab in AD cover this or do I need to make an edit in Exchange Management Console ?

Thanks for tip Vasil.

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Cliff GaliherCommented:
If the user has an exchange online mailbox, you need yo edit those settings in exchange.
paologiorgioAuthor Commented:
For (my) clarity....

EOL  = Exchange Online
EOP  = Exchange on Premise

Let's say a user is created in Local AD, the account is synced and Exchange license is added to the account in Office 365. Where do I set the primary SMTP ?

1. AD General Tab
2. Proxy Address Attribute of AD account.
3, EOL (if so where exactly ?)
4. EOP

I guess I'm confused that if they decommission exchange where would I make the change, I am confused as to why we are using exchange on premise to set Primary SMTP if we would not in the future ? So I am either reading your answer wrong or missing something.
Cliff GaliherCommented:
A hybrid deployment requires keeping an exchange management installation on-prem. You won't be retiring it. If you don't want to do that, a hybrid deployment is probably not a good choice.
Cliff GaliherCommented:
More information, and should fill in the gaps you seem to be missing:
paologiorgioAuthor Commented:
Thanks, but ignoring the part about me saying they may choose to decommission exchange in the future my above question is still not with a clear answer.  Thanks for info though.

Where do I set the Primary SMTP ?

Cliff GaliherCommented:
The very first sentence of my very first comment says "In an Exchange hybrid topology, all account management is done on-prem."

I can't make it any more clear. In a hybrid deployment, you *will* have an Exchange server (as I've said before and as the link I've posted goes into great detail on) unless you like breaking your environment. And since dirsync makes the source of authority the on-premises AD infrastructure, all Exchange related changes (including Exchange Online changes) are done from the Exchange tools on premises.  The changes will by synced up to Azure AD, and your Exchange Online mailbox will get the new setitngs you changed with the Exchange tools on premises.

So you make the changes in Exchange on prem, even though the mailbox is online.
paologiorgioAuthor Commented:
Dude, I'm asking the question because I simply don't know the answer. You have told me on premise which is great but you assume I know where in on premise to make the change. I have basically asked you where to make the change and I am getting throwback....because "you've made it clear"....we'll whoopdy do for you but alas I came to get clear answer and got.... "it's over there". I'll Google it so.  If I can manage to find my keyboard. I have never admined on-prem exchange 2010 btw.
Cliff GaliherCommented:
You are doing a hybrid deployment and you don't know exchange? I can't assume your level of knowledge and I'm not psychic "dude" so I'm not going to write a whole book just because you are out of your depth. If you've never managed exchange, you aren't ready for this project, no matter how detailed my answer. You need to go get training. Classes, books, etc. A forum answer will never be enough.
paologiorgioAuthor Commented:

A single line answer would have got me to where I needed to be. Yes, a Forum Answer would have been enough. Good Spiel though. Most enjoyable. You should consider becoming a leader or manager or teacher. You'd be fierce good at it. Nice guy too. Good man Cliff.

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