Exchange Online, part of Office 365, is essentially a really large implementation of the same components that customers would run on-premises. In the case of Exchange Online, Microsoft runs thousands of Active Director Forests to support its implementation of Exchange. In some cases, Microsoft may need to migrate or ‘shift’ Active Directory objects supporting Exchange Online between forests to rebalance the number of AD objects per forest. In most cases, this normal background maintenance goes unnoticed by customers.

Recently, we had a customer in the middle of a migration to Office 365 using our solutions while this type of background maintenance was being performed. The customer was reporting logon failures to Office 365 during the customers migration effort and we needed to investigate. During troubleshooting we realized that Exchange Online background maintenance was the root cause in this specific case. During our troubleshooting we learned from Microsoft how to determine when your Office 365 tenant was actually in the middle of such an event using PowerShell.

If you are experiencing logon failures to Exchange Online and would like to test if maintenance or ‘shifting’ may be the root cause, you can run the following PowerShell command. For information on connecting to Office 365 PowerShell – please see the following Microsoft article.

Get-OrganizationConfig | fl *region* 

The output from the above command – example shown below – according to Microsoft should return with no values. Empty values, as in our example, means your tenant is not currently being ‘shifted’. If you do show values, this could indicate your tenant is being ‘shifted’ and you can either wait or contact Microsoft for further assistance.

Output:

AllowedMailboxRegions              : {}
DefaultMailboxRegion               :
DefaultMailboxRegionLastUpdateTime :

Note: At the time of this posting, the information provided is believed to be accurate and useful. As Microsoft reserves the right to change its internal processes or procedures at any time we provide this information “as is”, with no guarantee of completeness, accuracy, timeliness or of the results obtained from the use of this information as outlined in our terms of use. If you are unsure or suspect you may be affected by internal maintenance, we encourage you to contact Microsoft support for further assistance and guidance.