Converting a Mail User to a Remote User Mailbox

I have an client with an existing Office 365 implementation and a separate on-premises Exchange organization. As part of linking these two together into hybrid mode, the local AD account became a Mail User.

A Mail User is a local AD account with an external SMTP address configured. This allows the user to have an email address in the GAL, but is not a local Exchange mailbox.

To move mailboxes, this Mail User needs to be configured as a Remote User Mailbox. A Remote User Mailbox also has a proper remote routing address property configured.

I couldn't find any documentation on performing this process. However, I did find a script that indicates it fixes up user accounts when a mailbox move to Office 365 does not complete properly. I used this script to identify the changes that needed to be made.

The script is here:
The changes that need to be made are:
  1. Configure the user attribute targetaddress to contain the remote routing address for the mailbox. This should be in the format of userid@domain.mail.onmicrosoft.com. In my case it would have been testmailbox@byronwright.mail.onmicrosoft.com.
  2. Set the msExchRemoteRecipientType attribute for the user account to equal 4.
  3. Set the msExchRecipientDisplayType attribute for the user account to equal -2147483642. (yes, this is a negative value)
  4. Set the msExchRecipientTypeDetails attribute for the user account to equal 2147483648.
Those steps changed the Mail User to a Remote User Mailbox. However, I was still unable to move the mailbox from Office 365 to the on-premises Exchange. This was due to the ExchangeGUID attribute not being set properly on the local user account. To fix this, I performed the following:
  1. In Office 365: get-mailbox testmailbox | fl ExchangeGUID
  2. In on-premises Exchange: set-remotemailbox testmailbox -ExchangeGUID 12345678-1234-1234-1234-123456789abc (note GUID is from step 1)
After setting the ExchangeGUID moves to the on-premises Exchange worked properly.

UPDATE: See a similar procedure for room mailboxes at: http://byronwright.blogspot.ca/2014/06/putting-office-365-room-mailboxes-in.html 

UPDATE: While the above seemed like a good procedure at the time. I've since become aware that you can use Enable-RemoteMailbox in this same scenario to fix up the local mail users to remote user mailboxes. For a script to do it on a whole OU, see here: http://byronwright.blogspot.ca/2014/10/script-to-resolve-error-when-running.html

Comments

  1. AnonymousMay 1, 2015 at 2:41 PM

    Thank you. This was very helpful!

    ReplyDelete
  2. BenNovember 7, 2016 at 7:52 AM

    Thanks for the helpful article.

    ReplyDelete
  3. AnonymousAugust 23, 2017 at 10:24 PM

    Thanks for the info. Be aware that if you are in hybrid mode then the enable-remotemailbox must be used along with the set-remotemailbox with the ExchangeGUId of the cloud mailbox being the parameter

    ReplyDelete
  4. AnonymousApril 3, 2018 at 2:34 AM

    Thanks man, doing steps A1-A4 also solved an issue for me where it was not possible to send a user mails from an external domain.

    ReplyDelete

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