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RevLV's avatar
RevLV
Copper Contributor
Apr 23, 2020

Email Deployment Issue

So I have backed myself into a corner with email migration to Office 365. I followed instructions from a vendor who sold us migration software, but it appears I am now in a bit of trouble.

 

The goal was a cutover migration from a single on-prem Exchange server.  We want to retire the on-prem server entirely and are not interested in running exchange at all on-prem.

 

The instructions indicated setting an attribute on the AD Sync tool to be null: https://www.codetwo.com/kb/msexchmailboxguid-problems/ which would allow the mailboxes to be created on Office 365.  That worked like a charm.

 

We used the software to migrate the content, repointed MX records.  At this point mail flowed properly into Office 365 and were able to repoint the clients.

 

All is working, EXCEPT:  we can't make any changes to mailboxes on Office 365 and we aren't able to retire our exchange server because it's being used to manage the mailboxes.

 

So I'm looking for a plan to fix this situation that won't break everything.  We seem to be stuck in between a cutover and hybrid migration and have gone non-standard.  

 

Before criticizing, please understand that I was following instructions from CodeTwo exactly. I realize its a mistake now, but I'm looking for a way out.

 

I have a bit of a plan, but I'm looking for feedback from the experts:

1. completely disable and uninstall AD Syn tool, which should allow the mailboxes to be managed on Office 365.

2. decommission the exchange server, which I'm thinking will remove all email/exchange attributes within AD.  AD will no longer be tied to Exchange for email in any way.

3. reinstall AD Sync tool which at this point will not be synching email attributes, allowing the mailboxes to continue to be managed on Office 365.

 

Any thoughts on this plan?

exchange
migration

1 Reply

  • Adam_Aardvark's avatar
    Adam_Aardvark
    Iron Contributor
    Apr 27, 2020

    Hi RevLV,

     

    CodeTwo's rep over here.

     

    Regarding the article you followed, please note that before migrating mailboxes you had to disable the synchronization of the msExchMailboxGuid attribute between on-premises AD users and Office 365 users. But even without this attribute Office 365 users are still synchronized with AD and that is why they need to be managed via on-premises Exchange. 

     

    If you have already deleted the mailboxes from your on-premises environment (or decommissioned the on-premises server), you need to disable directory synchronization to be able to manage migrated mailboxes through Office 365. Please see this KB article for details: https://www.codetwo.com/kb/managing-mailboxes-in-hybrid-environment/.

     

    All the best,

    Adam

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