Shared Mailbox disappeared after migration to O365 from EXC2010

Brass Contributor


I'm currently testing the migration of shared mailboxes from an exchange 2010 server to O365 with a hybrid deployment and the exchange online migration wizard.

First I created a user mailbox, converted it to a shared mailbox, synced this account to Office 365 and set up a migration batch for this mailbox only but after successfully completion the mailbox and its user accounts completly disappeared from Office 365.


Any ideas why this happened?

Thanks and regards!

4 Replies
Hi Julian,

Are you still able to see the mailbox in Exchange 2010 when you do a Get-Remotemailbox Powershell command?

And maybe this could be related to your mailbox not being synced because it's account is disabled.
You might want to check out this article:

This one could also be causing your problem:

@Julian12 do you get any output if you run Get-Recipient "your-mailbox" on-prem and in Exchange Online? And what are the user attributes in your on-prem AD for msExchRecipientType and msExchRecipientTypeDetails?


please make also sure that your on-premises mailboxes are discoverable and configurable through autodiscover process. You may also use the Microsoft connectivity analyzer for that purpose:

Hey Guys,
thnaks for your answers!
I checked our server and migrated Users again and recognized that the missing mailbox simply got a new email address whatsoever and hide it's real name between other mail addresses^^
The new primary address isn't even present in the proxyaddresses attribut in the on-prem AD and is even set to another shared mailbox in the AD.
I don't know why this occured, maybe some policies are doing this or the generell Exchange Online service corruption last week was making fun of me.

I will test again, maybe it is working now as expected.
Have a nice week!