Uninstall Exchange 2010 after Hybrid / Remove Move Migration. AD Sync already moved to a new AD server.

I need some assistance removing Exchange 2010 after a Remote Move / Hybrid Migration from SBS2011 before decommissioning the server and just leaving O365 in the cloud.   I might be overthinking the situation.

Original Setup - SBS2011 / Exchange2010
New Setup - Server 2016 Standard / Office365 Business - 80 mailboxes

AD Sync is currently setup on the Server 2016 box and working just fine.   All I want to be able to do is Sync AD Users and Passwords between the 2016 Server and O365 Business.  I no longer need Hybrid Exchange setup.  User gets setup in Local AD, creates the object in AzureAD - I assign the O365 license, setup the email address and go.  Future password changes stay synced between the Mailbox and local AD.

This is the first time I'm doing a Hybrid migration - I'm used to just doing a cutover style migration - once everyone is good in O365 I follow this guide to uninstall exchange - it's worked time and time again. - https://www.itpromentor.com/sbs-remove-exchange/

He does have another article with what appears to be my situation https://www.itpromentor.com/remove-hybrid-keep-sync/   but it sounds like some supported frameworks might have changed since.   Currently the SBS2011 box I have doesn't serve any function currently.

Is it safe to just uninstall exchange 2010 like I normally do following the cutover migration?
Fluid_ImageryAsked:
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Peter HutchisonSenior Network Systems SpecialistCommented:
Yes, I believe you just uninstall Exchange 2010 normally.

Microsoft does recommend keeping one recent Exchange 2016 server (or later) to allow you to add Exchange attributes to your AD accounts, as you cannot easily do that with the default AD tools except with ADSIEdit or Attribute Editor in ADUC or via scripts.

The main attributes you would need to set are:
mail, proxyAddresses, msExchRecipientDisplayType , TargetAddress
Alex AppletonBusiness Technology AnalystCommented:
You are going to need a local Exchange server still with AD sync in place.  Users will get created on premise still, and synchronized to cloud.
 Microsoft will give you an Exchange 2016 license for this, see here: https://support.microsoft.com/en-us/help/2939261/how-to-obtain-an-exchange-hybrid-edition-product-key-for-your-on-premi

There are documented ways around this with ADSIEdit, but you may run into support issues if you go down that route.  I'd suggest firing up a small VM with Exchange 2016 on it before retiring your 2010 server.
Fluid_ImageryAuthor Commented:
Thanks for the replies.  The link didn't work can you try resending?   Do you have a documented way to install Exchange 16 for management purposes.   My local exchange install knowledge expired in version 2010 when I began upgrading everyone to hosted exchange.

Sounds like my options are:
1 - Fire up a Server 2016 instance and install Exchange '16 for management purposes - supported
2 - Basically just turn off SBS2011 box and leave orphaned Mail Attributes in AD then use 3rd party utility or ADSI - Not supported
3 - Seems like a pain - but run the MSOL command to kill the AD Sync and put the Mailboxes back "in cloud" would need to re-add any aliases and distribution groups. Then set new passwords and have users attempt to reset them back to their original.

If I uninstall Exchange 2010 currently it will most likely nuke the Office365 environment when AD syncs again post removal.
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Alex AppletonBusiness Technology AnalystCommented:
1 is best, 2 is fine but remember that any new users you will need to create on premise so you would have to create those attributes manually using ADSIEdit and allow for those attributes to sync to cloud.  

Check out this link, gives more detail on how to obtain the license key:  https://blogs.technet.microsoft.com/exchange/2018/07/20/hybrid-configuration-wizard-and-licensing-of-your-on-premises-server-used-for-hybrid/

Installing Exchange would be the same as if you were installing it full bore, except you don't have to concern so much about setting DNS records and such.  Also, migrating mailboxes should be excluded because you already have them in cloud, but you may have to migrate the system mailboxes and arbitration mailboxes that are likely still on your 2010 server.  Probably the best write up for 2010 to 2016 is here:  https://www.kerneldatarecovery.com/blog/step-by-step-guide-for-migrating-exchange-server-2010-to-2016-part-1/  

One tip I can give you is that when 2016 is up you'll probably want to set the Autodiscover service URL on prem to null to avoid your clients reaching out to the on-prem server  by running the following command:
Set-ClientAccessServer –Identity “SERVERNAME” –AutoDiscoverServiceInternalUri $NULL
Fluid_ImageryAuthor Commented:
Thanks.   I'm on the fence - I would like to get away from any local dependency of Exchange all together.  I feel like Microsoft is going to release some other supported way to do this instead of either leaving the SBS2011 or migrate Exchange 2010 to a new VM with 2016.

I'm 75% on the #2 route approach of just turning off or uninstalling Exchange 2010.
- What will happen if I uninstall Exchange 2010 on the SBS2011 server as I would typically with a cutover migration?

When I create a new user now - I just create them in local AD and let it sync - then assign the O365 license in the cloud along with any alias addresses etc.  I don't ever open EMC to create a mailbox.   When I look in the console as it is now none of the mailboxes are there, only the ones I didn't migrate over because they aren't needed.

Reading through this - https://techcommunity.microsoft.com/t5/Office-365/Remove-On-Premises-exchange-Hybrid-and-go-fully-Online/td-p/143255

It doesn't seem like it's going to effect the cloud environment at all.  But then I've read on other sites that if I remove Exchange it will clear the Mail Attributes in ADUC and nuke the exchange mailboxes in O365.
Peter HutchisonSenior Network Systems SpecialistCommented:
The Exchange EMC can be used to create Mail Enabled Users or Remote Mailbox Users rather than just Mailbox Users.

How are you creating the user AD? Do you set any of the mail or msExch attributes?

What attributes do your existing AD user have, that have Office 365 accounts?
Fluid_ImageryAuthor Commented:
If I click over to the Attribute Editor tab on ADUC

Check the most recent user I've added - post initial migration

None of the msExch... attributes are set.
Mail attribute is set to the email address
UserPrincipalName is set to the email address

A user that existed in AD during migration has:
legacyExchangeDN set to - /o=First Organization/ou=External (asdfasdfasdfasdf)/cn=Recipients/cn=asdfasdfasdfasdf
Mail set to email
msExchMailboxGuid - set to characters string
msExchMobileMailboxFlags - 1
msExchangePoliciesIncluded - set to character string
msExchRecipientDisplayType - set to -2147483642
msExchRecipientTypeDetails - set to 2147483648
msExchRemoteRecipientTYpe - 4
msExchSafeSendersHash - \F8\34\29\18
msExchTextMessagingState - set to numbers
msExchUMDtmfMap - set to emailAddress: numbers firstname / lastname
msExchUserAccountControl - 0
msExchVersion - 44220983382016
msExchWhenMailboxCreated - set to date string

ProxyAddresses set to his local and x500 addresses
targetAddress set to built in .onmicrosoft.com address
Peter HutchisonSenior Network Systems SpecialistCommented:
That seems reasonable. Before completely removing Exchange. I would make sure you have an up to date backup of AD database on the DC.

See these scenarios that may help:
https://docs.microsoft.com/en-us/exchange/decommission-on-premises-exchange
Alex AppletonBusiness Technology AnalystCommented:
"I feel like Microsoft is going to release some other supported way to do this instead of either leaving the SBS2011 or migrate Exchange 2010 to a new VM with 2016." - here's hoping.  I feel they need to.

"When I create a new user now - I just create them in local AD and let it sync - then assign the O365 license in the cloud along with any alias addresses etc.  I don't ever open EMC to create a mailbox.   When I look in the console as it is now none of the mailboxes are there, only the ones I didn't migrate over because they aren't needed." - This is not the correct way to do this.  Typically the process would be to create the user in AD, then run the powershell "Enable-RemoteMailbox" command.  By doing it that way you are likely to have problems (see: https://support.microsoft.com/en-us/help/3129334/users-in-a-hybrid-deployment-can-t-access-a-shared-mailbox-that-was-cr for example)

Here's some good documentation from Microsoft on this:  https://docs.microsoft.com/en-us/exchange/decommission-on-premises-exchange
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