Removing an Exchange 2013 Schema Prep

How to un-prepare an AD Schema after preparing it for Exchange 2013.

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Ok, best start this with a…

DISCLAIMER: Doing this sort of stuff on a live system should be taken very seriously - be very careful. I’ve done this on my demo environment as I wanted to run an Exchange 2010 install on a system that had already being prepared for Exchange 2013. It does work, and it works well…would I do it on a live topology? Not if I could possibly get out of it, no.

Main Article
After you’ve done an Exchange 2013 Active Directory preparation, you may have reason to want to remove it. Let’s say you’ve realised you still need to implement other servers (like Exchange 2010 for example), or the installation went wrong, or ….insert your own reasons here.... It is possible to do, you just need to run through a few steps.

Remove Users
The first thing you need to do is delete some users that the prep routine would have set up. These are:

*SystemMailbox
_plusGUID
*HealthMailbox
_plusGUIDDiscoverySearch Mailbox_plusGUID
Exchange Online-ApplicationAccount
FederatedEmail.
_plusGUID
Migration.
_plusGUID

Get rid of those. Note that the name will start as above but a number of them end with a GUID - if you don’t know what that is, you probably shouldn’t be doing this….

Use ADSIEdit
Again, if you don’t know what ADSIEdit is, you probably shouldn’t be following this process. These are the things you need to remove:

Configuration Context
Delete the following items:

CN=Microsoft Exchange Autodiscover,CN=Services,CN=Configuration,DC=
domain,DC=local
CN=Microsoft Exchange,CN=Services,CN=Configuration,DC=
domain,DC=local

Scared yet…?

Default Naming Context
Delete the following entries:

CN=Microsoft Exchange Security ObjectsCN=Default naming context,DC=
domain,DC=local
CN=Microsoft Exchange Security Groups,CN=Default naming context,DC=
domain,DC=local

Summary
It’s not that hard to remove critical entries from the AD Schema so you can then go on and do other stuff - like install Exchange 2010 for example - but, on the other hand,
it’s not that hard to remove critical entries from the AD Schema. So, be careful!

Like I say, happy to do this on my demo environment - in production, I’d avoid it if at all possible. It certainly isn’t a supported option from Microsoft.

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