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:
- 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.
- Set the msExchRemoteRecipientType attribute for the user account to equal 4.
- Set the msExchRecipientDisplayType attribute for the user account to equal -2147483642. (yes, this is a negative value)
- 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:
- In Office 365: get-mailbox testmailbox | fl ExchangeGUID
- 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