Delete System and Arbitration Mailboxes after Office 365 Migration

Hey all,

We successfully completed our migration of all user mailboxes from our on-premise Exchange 2010 server to Office 365, and would now like to decommission the on-premise Exchange 2010 server. We have a separate server that we are leaving on-premises for management, which only has the EMC and no mailbox role. But the old mailbox server should be decommissioned now. It has been turned off for weeks with no impact. We have removed the hybrid configuration. MX records and autodiscover are all moved. DirSync is in place and working.

When attempting to uninstall Exchange 2010 from the old mailbox server, we are getting the error "This mailbox database contains one or more mailboxes, mailbox plans, archive mailboxes, or arbitration mailboxes." and cannot continue. The error suggests either moving the arbitration mailbox or disabling the mailbox if this is the last server in the organization. Since we don't have any other mailbox servers, there is nowhere to move it. And disabling the mailbox makes me nervous because though this is the last on-premise server, I don't want this to affect our cloud services by assuming we are decommissioning the organization. What do we do with the system and arbitration mailboxes?

We have read the article here but it does not fulfill our specific need: http://blogs.technet.com/b/exchange/archive/2012/12/05/decommissioning-your-exchange-2010-servers-in-a-hybrid-deployment.aspx

Also, and I'm not sure if this is a separate topic, how can we make sure that removing this on-premise mailbox server will not remove mail attributes from our user objects?

Thanks!

September 10th, 2015 11:08am

Well if this is your last server and you have shut it down for a week or so and if there is no impact why worry,

Get the mailbox which is on the server, if it is arbitration mailbox then just disable it and decommission the server

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September 10th, 2015 11:16am

Well, it's the last on-premise server, but there are cloud servers running our mailboxes now. I don't want this to break our organization as a whole. The message suggests running the Disable-Mailbox command using the parameter "-DisableLastArbitrationMailboxAllowed" but I'm nervous that this will trigger something in Office 365 to make it think we're decommissioning the organization. I cannot risk breaking email for my company. What do you think? Thanks.
September 10th, 2015 11:21am

Hi darioism,

Thank you for your question.

By understanding, you turn off Exchange on-premise for few weeks with any problems and have moved all mailbox to Exchange online, so we suggest you delete the system and arbitration mailbox, then uninstall the Mailbox role.

If there are any questions regarding this issue, please be free to let me know.

Best Regard,

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September 10th, 2015 10:30pm

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