Service Domain Prefix Appears and Disappears in Exchange Online Cmdlets

Where Did that Service Domain Come From?

In early January, some Exchange Online administrators noticed that the tenant service domain was listed in front of the output from several PowerShell cmdlets. For example, if you ran the Get-RetentionPolicy cmdlet to return the set of mailbox retention policies know to Exchange Online, you’d see something like this:

The service domain also showed up in mailbox properties when viewed through the Exchange Admin Center (EAC).

Figure 1: Tenant domain prefixes show up in EAC

A Quick Reverse

When Microsoft was asked why the cmdlets included the service domain, it emerged that this was an unexpected side-effect of a change made to solve a problem. Microsoft later reversed the change and the cmdlets ceased outputting the service domain on January 7.

Everyone can appreciate that code changes are sometimes necessary to fix problems. What’s not so good is the obvious lack of testing and control that allowed the update to be introduced into Exchange Online without understanding what effect this might have. For instance, although PowerShell scripts continued running and were unaffected by the change, it’s possible that changing the output of a cmdlet could wreak havoc on a tenant’s operational processes.

Likewise, when a cmdlet starts to behave differently after years of stability, it causes heartburn for administrators and help desk staff who don’t know why this might be the case. And of course, documentation based on the earlier behavior needs to be updated.

Even Well-Intended Changes Need Testing

I’m sure that the change was valid and did what it was supposed to do. However, allowing a change to proceed into a service that has hundreds of millions of users without full testing is just unacceptable. Let’s hope that this was a minor blip in Microsoft’s quality control and change management systems.


This is the kind of change that the Office 365 for IT Pros team keeps an eye on… and lets you know if we think it’s important. With over 1,400 pages of content between the main book and companion volume, there’s a heap of detail to master in Office 365.

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