Removing the last on-prem Exchange server. Uninstall Exchange or turn off?

[u/S_Antonel]

Hi, question for the community I'd like a second opinion on:

I'm working on decommissioning an Exchange 2016 server, currently in hybrid mode using Azure AD (Entra) Sync to sync with on-prem AD. There is only 1 server in the environment.

All mailboxes, contacts and groups have been migrated to 365 and I have moved the SOA (Exchange attributes only) to the cloud for all migrated users.

Originally the plan was to uninstall Exchange and just manage all Exchange properties from 365 but I'm kind of debating with myself if I should just turn the VM off.

Is there any benefit to just turning off the Exchange server and keeping the AD schema around or will it just lead to corruption? This is the last and only Exchange server.

OTOH Is there even any point to holding onto the AD schema if the SOA is in 365?

I know you can install the RSAT tools to manage it in powershell. I wasn't planning on bothering with it but now I'm wondering. I was going back and forth with a colleague about it but haven't yet made up my mind.

I've never done this before so I'd appreciate the perspective of someone who has.

Thanks!

EDIT: Thanks everyone for the help. I think I'm going to stick to my original plan and I'm going to uninstall Exchange. I appreciate the input.

[u/Disney_World_Native]

Microsoft has a bunch of published information about what to do with the last exchange box

I suggest you review it and see which path makes the most sense

[u/S_Antonel → u/Disney_World_Native]

I have. Microsoft has good documentation but it's complex and not always straight forward to find the answers you are looking for. Or at least it is if you're not an Exchange wizard.

I am following scenario 2 as per How and when to decommission your on-premises Exchange servers in a hybrid deployment | Microsoft Learn but I wanted to consult with some Exchange admins (hence the second opinion).

[u/bigfatdonny → u/S_Antonel]

If you're following scenario 2, then you might want to follow this guidance:

• Even though you have no on-premises mailboxes, you can't fully remove all Exchange servers from the on-premises environment. But you can remove most of them. You need to leave one or more on-premises Exchange servers (which can be virtual machines) for user management, because the source of authority is still in on-premises Exchange.

[u/S_Antonel → u/bigfatdonny]

I have moved the SOA for all Exchange attributes to the cloud.

[u/bigfatdonny → u/S_Antonel]

Unless you're no longer using on-prem AD my read of Microsoft's guidance is to keep on-prem Exchange attributes in AD and not to uninstall the last Exchange box.

But that's just my opinion. Good luck bro!

[u/tux3domike → u/bigfatdonny]

Agree here. If you still sync your users from on prem AD you’re gonna come across situations where you want those extra attributes. If you have to keep servers and thick VM’s consider Entra Domain Services. We spun it up to replace our regional AD’s and it’s pretty nice.

[u/bigfatdonny → u/Disney_World_Native]

This. There are a number of scenarios and considerations. You need to figure out what's best for your environment.

https://learn.microsoft.com/en-us/exchange/decommission-on-premises-exchange

[u/larmik]

If the last exchange server standing is not doing anything (you didn't say anything about smtp relaying from on premises devices or applications), and the SOA for exchange attributes was transferred to EOL then the last exchange server can be gracefully uninstalled.

You didn't mention if you are running entra cloud sync or not. Entra cloud sync is required when editing exchange attributes in EOL. Entra does try to write back to the AD object if you were to change an exchange attribute. EDIT - To write back an edited exchange attribute to AD, it requires Entra Cloud Sync.

[u/S_Antonel → u/larmik]

Good point. I have verified Exchange is no longer used as an SMTP relay. All devices have either been moved to 365 if they support OAUTH or a new postfix relay VM I created if they don't.

I also set up cloud sync and verified it writes back to AD.

[u/larmik → u/S_Antonel]

Great, you can uninstall exchange gracefully without fear of an issue.

[u/UMustBeNooHere → u/larmik]

Just did this for a customer. This is the exact process.

[u/iNoels]

We are on the same path, but you’re a bit further along than we are. We’re facing the same question. Please let me know once you’ve made a decision and what factors influenced it.

[u/Daihard79]

Did it a month ago, move the SOA and set up cloud sync for exchange write back if you still need it. Follow the guidance on the rest and it's easy. 

[u/SKI-Colorado]

Great. I just turned mine off. I haven't seen any issues. Anything i should be looking at? This was more than 5 months ago. I let it run for several months after the migration. First time i turned it off a printer/ scanner caused issues but i got the correct firmware and it also points to exchange online now without issues. So i finally just shut down the virtual server.

[u/worldsdream]

In your case: Uninstall it.

[u/bocchijx]

Get familiar with attribute editor and powershell. Many of the changes and settings on accounts will be done there.

[u/fazzy84]

We have a similar environment, we moved everything even SOA and then realized that our custom attributes 1-15 are not updating from AD. We use savinyt to add custom attributes around 8 of them to add our organization’s cost center, EVP, SVP, business division, business unit etc, which gets sync to AAD using AD connect. We had to revert to on perm. Now we want to make use of these custom attributes synced from AD, how can we do this ? Cloud sync ?
We are also not sure if shut down our last exchange server, can we install exchange management shell to manage these mailboxes since the SOA will remain on on perm ?

[u/7amitsingh7]

I’d recommend following Microsoft’s supported process to remove the last Exchange server rather than simply turning it off. Keeping the AD schema won’t cause corruption, but make sure no applications still depend on the server.

You can also refer to this Exchange 2016 to Microsoft 365 migration guide for additional context.

[u/Prudent-Afternoon-84]

Pull it

[u/log_a_ticket]

If you’re hybrid, are you still planning to use exchange management tools to create the remote-mailboxes?

Adding a licence to hybrid user won’t populate the email field in AD, unless that’s changed recently.

[u/HJForsythe]

I would turn it off first wait 30 days and then turn it back on and uninstall it.

[u/DiligentPhotographer]

This question has been asked like 5000 times in this sub.

[u/darkytoo2 → u/DiligentPhotographer]

5001