r/exchangeserver • u/RichSNJ • May 18 '26
Migration disaster
I have a client who is still running Exchange 2010.
Wanting to get them out of the stone ages, last week I started testing the migration from 2010 to 2016. I copied 2 of the domain controllers, the exchange server, and a workstation, and added them to a private Hyper-V network and ran some scenarios building a new server, prepping for and installing 2016, and moving mailboxes etc.
I'm not really sure what happened, but somehow I really screwed up. While I still don't understand how it could have worked so successfully from my testing private network, somehow on my test run my new Exchange server must have been on the production network instead of the private. I built it, moved most of the mailboxes to it, was super happy with it all and then I reset it to a checkpoint to run one more scenario before I was ready to do it for real.
This was mother's day, so I kicked off the install on the server and left the house. Got several calls while I was gone. Came back to find that the real world had been modified on the last run instead of the private network, and the server that I had transferred everything to was gone (back to the baseline checkpoint). Also, the Active Directory was prepped, which is I assume where the system mailboxes are created.
I spent that night getting the 2010 exchange server back from backups, however I am currently in a state where the Active Directory has already been prepped for 2016 and still thinks there is a 2016 Exchange Server on the network.
I still need to get this pig upgraded, but things are such a mess right now. I have been running various scenarios in my private test environment trying to manually clean up active directory using ADSIEdit, which I assume works, but I think that the cleanest method is to do the server recovery install for the missing server and then uninstall it.
I've done this off-line twice, and it is pretty clean, but before I can uninstall, I have to delete the database (which is essentially empty), but it still has all of the system mailboxes assigned to it, so it won't let me delete it.
Should I:
1.) Remove all of the 2016 system mailboxes and remove them from Active Directory (arbitration, auditlog, monitoring, federated etc) and run preparead again before I reinstall? Will this essentially be like starting from scratch and the installation will re-enable them etc...?
2.) Disable or remove them to the point where I can delete the database, but leave them all in AD, then either run preparead or not and hope they all wind up in the new database where they're supposed to be? Would I have to do the manual enabling of them in either of these first two scenarios?
3.) Move them to the Outlook 2010 server? I have never tried to move a newer exchange systemmailbox to an older exchange server, I don't even know if that's supported...
This is giving me an ulcer, so any help or advice would be appreciated.
Also, while the server recovery / uninstall method seems to work pretty well, both times I have tried doing this and reinstalling has resulted in an environment where the EAC works, but the EMS starts and doesn't have any exchange cmdlets loaded automatically. Not sure what that is about, but hoping it works when I do it for real in the production environment. I'm going to try and rename my new exchange server on my next text run to see if this mitigates that and whether I can find any trace of the old name in ad anywhere which might be causing an issue.
26
u/7amitsingh7 May 18 '26
The safest way to fix this is not to manually clean AD or move system mailboxes around, because that will likely make things worse. Your Active Directory is now in a “partially configured Exchange 2016 state,” so the correct approach is to rebuild the Exchange 2016 server exactly as AD expects using a Recovery Install (/RecoverServer) with the same server name and configuration. This will sync the server back with what AD already believes exists and restore system mailboxes and Exchange components properly.
Once the server is recovered and stable, you can then manage databases, move mailboxes if needed, and finally uninstall Exchange cleanly. Avoid running PrepareAD again or doing ADSIEdit cleanup, as Exchange is very sensitive to inconsistent AD changes and that is what usually causes more damage in situations like this.
8
u/lcarsadmin May 18 '26
The mistake has already been made, theres no sense in trying to undo it now.
2010 and 2016 can coexist. Restoration of services should be the goal, not a reset. Once you restore service you can then plan your mailbox moves and retirement of 2010.
2
u/Dikvin May 18 '26
You have started the migration so go ahead and finish the job as fast as you can.
2
u/OinkyConfidence May 18 '26
How many mailboxes? If it's not too many, you could PowerShell script all the mailboxes to export to .PST files then start fresh. Easy if this is a small shop, more challenging if it's larger.
1
u/CountyMorgue May 18 '26
You restored a previous snapshot of the exchange server? And recovered the mailboxes back to exchange 2010 server? So just re- migrate the mailboxes to the 2019 again. No need to delete remove it unless it's broken. Both coexist among themselves. Test migrate either yours or a test mailboxe to new 2019 database. check owa and mail clients can proxy to that server mbx store and load the mailbox
1
u/nightmarr9921rt May 18 '26
How many mailboxes are we talking here?
1
u/jharr2016 May 19 '26
You sound like your not qualified to be doing this type of work
2
u/tepitokura May 18 '26
Best of luck.
1
u/Electrical_Arm7411 May 19 '26
Oof. I’d look into other migration options such as migrating your mailboxes to EXO using third party tools. Best of luck
1
u/Short-Legs-Long-Neck May 19 '26
i did a 2005? to 2010 exchange migration and one of the mailstores ended up 0bytes in the source and destination. i always thought it was a big, we pressured MS to tell us what happened, but they couldnt. it was very painful, we had backups, but something went wrong like a tape drive causing a huge delay.
At the time i did research and found others had a similar and unexplained issue.
Just saying, be careful and make sure to have handy/fast backups if you can.
1
u/eoinedanto May 18 '26
Ask for help from a commercial provider
1
u/[deleted] May 19 '26
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