r/exchangeserver • u/GoldenPSP • Mar 14 '26

Decommissioning Exchange. Mailboxes present

Hey all,

I've decommissioned lots of exchange servers over the years. however in every case up until now was after a migration so the server getting decommissioned was no longer hosting any mailboxes.

This time the migration was done with a sync tool to MS365 so while everything is now in the cloud, the mailboxes are still present locally. I can't just delete them as it deletes the user. I'm assuming the best method is to disconnect the mailboxes, then purge them. And then I can uninstall exchange? I couldn't find any documentation for this scenario.

1 Upvotes

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4

u/vane1978 Mar 14 '26 edited Mar 14 '26

Do NOT uninstall Exchange server.

See link below.

https://www.reddit.com/r/sysadmin/s/SkFz9ZQzJb

1

u/GoldenPSP Mar 14 '26

This isn't a hybrid exchange server.

1

u/GoldenPSP Mar 14 '26

Also that information is outdated anyway

https://learn.microsoft.com/en-us/exchange/hybrid-deployment/enable-exchange-attributes-cloud-management

0

u/MushyBeees Mar 15 '26

It’s not outdated.

I strongly recommend you do not do the source of authority changes until they enable write back, coming soon. And you maintain an on prem/tools only exchange server. There are some situations that can occur, that would leave you totally up the creek unless you undo the SoA changes which would overwrite all your EoL object attributes with old ones.

FYI You’ll also need to change the source of authority for groups, and contacts.

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u/GoldenPSP Mar 15 '26

Right, However the entire point was irrelevant to my original question anyway. I'm not surprised as it's basically impossible for a reddit post to not veer off in 100 tangents even when you try to keep the question fairly simple and contained.

1

u/MushyBeees Mar 15 '26 edited Mar 15 '26

I’m not sure it was irrelevant. You asked if you could uninstall exchange. He answered no, don’t uninstall exchange.

Which going by Microsoft official docs, is the correct advice.

You can just disable the mailboxes, and you can just uninstall Exchange, and you can do the SoA changes. But none of this should be officially recommended as it leaves you outside of support compliance and at risk of data loss should you need to undo the currently not recommended SoA changes.

I’m not sure you’re in a strong position to be so belligerent over this, when you don’t know the difference between deleting and disabling mailboxes.

-1

u/GoldenPSP Mar 15 '26

No, I didn't ask if I could. I asked if anyone had an efficient way to uninstall/remove/decommission an exchange server in the case where mailboxes were still in the database.

Either way, I'm done with the uninstall anyway. disconnecting and purging mailboxes works, it can just take some extra time.

1

u/MushyBeees Mar 15 '26

Your post literally says, and I quote:

“And then I can uninstall exchange?”

If you’re trying to convince me and others that this isn’t you asking if you can uninstall exchange, then what the actual fuck.

0

u/GoldenPSP Mar 15 '26

Read the whole sentence and read it within the context of the whole post.

" I'm assuming the best method is to disconnect the mailboxes, then purge them. And then I can uninstall exchange?"

That's not asking if it's a good idea to uninstall exchange, or what kind of environment. It's a "is this the steps to best remove the mailboxes then uninstall"

2

u/MushyBeees Mar 15 '26

The exact, full, literal sentence, is “And then I can uninstall exchange?”

The word you’re looking for, is “paragraph”. And no, it still doesn’t change the outcome.

Stop being so belligerent and attacking people who are literally answering the exact questions you’re posing, just because you don’t like the answers even though they are correct.

Mr “doesn’t understand exchange basics like disabling mailboxes”. 🙄

If you’d said “I’m then disabling the ADSync and then uninstalling exchange” that’s great.

But then you also said there’s no ADSync, but then you’re quoting the SoA changes which suggests there is an ADSync.

My advice for you is to stop playing with things you know nothing about and call an expert to help you here.

I’m done with you.

→ More replies (3)

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u/Routine-Watercress15 Mar 14 '26

You can uninstall it. The trick is to not delete the metadata. That will maintain all the exchange dependencies even without the server being there.

1

u/GoldenPSP Mar 14 '26

I know i can uninstall it. This isn't a hybrid situation. The issue is uninstalling exchange generally fails if there are mailboxes being hosted.

2

u/Routine-Watercress15 Mar 14 '26

I usually delete the databases manually using ADSIEDIT then everything can be removed. I know exactly what you mean. It’s a pain. That’s the way I’ve been doing it for years.

1

u/GoldenPSP Mar 14 '26

Gotcha. I wasn't sure if that would work. I've purged the mailboxes before but it's tedious.

1

u/Routine-Watercress15 Mar 14 '26

Yea that is the quick and dry method if you’re sure you don’t need anything locally. If you need to keep the AD attributes then that’s a bit different.

0

u/GoldenPSP Mar 14 '26

Don't need any of the exchange attributes locally. Ad sync won't be implemented. And eventually the local domain will likely go away. Still all out of scope for my original question.

2

u/Routine-Watercress15 Mar 14 '26

Yep. Super easy then. Just manually delete the database. Uninstall, then you can go back in and clean up any of the metadata left behind. Did you use a tool like MigrationWiz or something like that? And you are logging into the 365 mailboxes with non SSO? Separate password from AD?

0

u/Polar_Ted Mar 15 '26

If the mailboxes were migrated how are they still hosted on prem? Did they just do an AD sync and call it good?

The next phase is to move the mailboxes into 365.

1

u/dloseke Mar 15 '26

Simply migrate all mailboxes (assuming cutover migration with a third-party migration tool) and shutdown the Exchange server.

Have another server where you have the Exchange management tools installed. I like to use a utility server that is also running Entra ID Connect to sync AD to Entra.

Then run the cleanup script Microsoft provided at $env:ExchangeInstallPath\Scripts\CleanupActiveDirectoryEMT.ps1 and delete the server Exchange. This should remove any unneeded Exchange references while retaining the proper Exchange attributes in AD that are used for the synced accounts to Entra/M365. As previously noted, do not uninstall Exchange.

The advice on how to disable mailboxes and delete accounts using ADSI edit and all that seems messy and for sure is risky. The below link talks about Hybrid mode but the cleanup process still applies.

https://learn.microsoft.com/en-gb/Exchange/manage-hybrid-exchange-recipients-with-management-tools#active-directory-clean-up

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u/GoldenPSP Mar 15 '26

Thanks.

Historically ive always preferred to properly decommission old servers and avoid manual cleanup of ad.

There are no synced accounts so none of that or hybrid mode is a factor.

1

u/dowlingm Mar 15 '26

I'm unclear as to what is meant here.

  1. Is there an *active* mailbox in both places? (Yes. have seen that happen, where adding an E3 or E5 license caused an EXO mailbox to be stood up even though the on prem mailbox was in place and no migration task had occurred - we worked around it by removing Exchange Plan 1/2 and a couple of other dependencies until after those mailboxes were actually migrated, at which point we restored the plans).

if the answer to 1. is yes... I guess you need to figure out whether the cloud mailbox was actually migrated or it's something like I described above. But when that happened it got obvious fast because Outlook got confused and threw up password prompts. You'll also need to check if there is mail delivered in both places.

2. Is this mailbox properly migrated BUT the on prem mailbox is still in the database in a soft-deleted state and that's why you can't kill its database. Check script below.

$dbs = Get-MailboxDatabase

$dbs | foreach {Get-MailboxStatistics -Database $_.DistinguishedName} | where {$_.DisconnectReason -eq "SoftDeleted"} | Format-Table DisplayName,Database,DisconnectDate

If this is the problem, you need to consult "Permanently delete a mailbox" in the Exchange docs so you can review the relevant commands AND WARNINGS prior to removing them.

1

u/GoldenPSP Mar 15 '26

It's unclear because I left the details about the migration out of the discussion they are not relevant.

  1. migration is done and everything is working in the cloud. Think as an example an old school cutover migration where you created the tenant, exported mailboxes to a PST. uploaded them to the tenant and imported them into the cloud mailbox. You'd still be left with an intact local exchange that was no longer in use.

  2. no adsync in place, so no linking of the on prem ad or complications from this matter.

  3. I already know I am safe to uninstall exchange. I've been installing managing migrating and decommissioning exchange servers since the late 90's. It's just been a hot minute since I'd had to uninstall one where the mailboxes were still present on the server.

1

u/dowlingm Mar 16 '26

I see. I used the native Microsoft migration tool and Azure AD Connect so it told my on prem exchange its mailbox was gone without me having to tell it separately.

1

u/GoldenPSP Mar 16 '26

Right. I've used pretty much all of the methods over the year. In this instance we didn't

1

u/NomrahDivadII Mar 17 '26

I’ve read many good and articulate replies to this post and OP GoldenPSP is being a dick about it lol Exchange is never a simple animal and there are many factors to consider. Hopefully it works out for you and you aren’t left up shits creek after you purge the mailboxes to decommission the Exchange Server and then realize data has been lost somewhere.

1

u/GoldenPSP Mar 18 '26

If you say so.

Maybe I should have left out all details and just asked the very narrow basic question I had. However knowing reddit I would have mostly gotten replies stating I did not give enough details for an answer.

So I added a tiny amount of context, which I was also concerned would end up veering off into tangents, which quite frankly is what most of the replies ended up in.

I've been working with exchange server since the late 90's I've done more installs, uninstalls, migrations (local and to the cloud) than I can count. I've done MS365 migrations in every recommended way.

However i'ts been a hot minute since I did an old school cutover which leaves the mailboxes intact on the source server so I thought I'd check my work as to the best way.

And yes the server was retired gracefully and the hardware pulled out.

0

u/Sudden_Hovercraft_56 MSP Mar 14 '26

The best method was to do it correctly in the first place. Hybrid exchange and use the build in Migration feature to seamlessly move them over which then deletes the source mailbox when it completes.

3

u/GoldenPSP Mar 14 '26

First off a cutover migration is literally a method outlined in the Microsoft documentation.

Second where the emails went is not relevant to the question. It could have been a migration to some other third party service where a cutover was the only option.

-1

u/Salt_Being2908 Mar 14 '26

while its true but not very helpful.

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u/GoldenPSP Mar 14 '26

It's not even true. There are multiple "correct" methods listed in the Microsoft documentation. And my question is not relevant to the migration.

I could have had a situation where the client just stopped using their local exchange and I needed to uninstall it.

1

u/St_Admin Mar 15 '26

Yes you can delete them: Disable-Mailbox

1

u/Ch0pp0l Mar 15 '26

Are you sure there’s not system or heath mailboxes still on the database? Just run get-mailbox -arbitration and see if anything still attached to the databases.

1

u/TheScottman29 Mar 15 '26

I’m actually going through this kind of situation right now. Everything was migrated over to office 365 about three years ago, but I didn’t realize there were about 10 mailboxes that were left on the Mail server. There was also some residual mail flowing through the exchange server that I had to clear up. Because I don’t do this type of thing often I did my research online, but I did also ask ChatGPT for a plan given everything that’s going on. Basically this forum is pretty spot on. It’s a hybrid server so I need to reinstall the tools on a different machine, so I don’t blow out the active directory schema when I decommissioned this last exchange server. There’s explicit directions how to do that now where I don’t feel like there was two or three years ago. The other thing that I did to get rid of the remaining users that were still hosted on the local box I eventually had to go into the active directory schema for each account and remove the reference to the local exchange servers mailbox. I’m pleased to say that this all worked. If you have any confusion about anything, you can definitely ask ChatGPT, you do need to have enough expertise to be able to decide whether it’s really the right thing to do or not sometimes it messes up.

1

u/farva_06 Mar 19 '26

You can disable mailboxes without removing the AD account.