Do I Need to Upgrade Distribution Groups When Upgrading Exchange 2003 to Exchange 2010?

1. Clicked the General tab
2. Removed the last character of the Distribution Group’s name
3. Typed in the last character of the name again
4. Clicked Apply

Revolutionize Your Business With Generative AI

From product design and software development to virtual agents, content creation, and reporting, GenAI is transforming business. Our AI experts help you unlock GenAI’s full potential and drive growth.

Let’s Get Started

When I clicked Apply, I received the following popup:

I clicked Yes and all was well. It appeared that the Distribution Group was “upgraded” and the settings on the Membership Approval tab were no longer grayed out:

Discussion:
While the steps above resolved my immediate problem and activated the settings on the Membership Approval tab, I’m not entirely sure why it worked or why it needs to be done. I have searched for information regarding whether or not Distribution Groups need to be “upgraded” after introducing Exchange 2010 SP1 Servers into an Exchange 2003 Organization without any success. While I have not been successful in finding any Microsoft documentation relating to this, I have several customers who are receiving this popup when modifying Distribution Groups using the Exchange 2010 Management Console. It makes sense that Distribution Groups might have to be upgraded to Universal Groups (especially in multi-Domain environments), but I have seen this behavior on Distribution Groups whether they are Universal or Global.
Some of my customers have also reported that some of their Distribution Groups don’t function correctly or can’t be used unless they are “upgraded”. I find it very odd that a Distribution Group created in an Exchange 2003 environment would need to be “upgraded” before it can be fully administered and used in a mixed-mode or native Exchange 2010 environment, but this appears to be the case.
Resolution:
The Background section above provides a way to manually “upgrade” Distribution Groups using the Exchange Management Console. The following PowerShell Command will perform the same function:
Get-DistributionGroup –ID “DistributionGroupName” | Set-DistributionGroup –ForceUpgrade
To “upgrade” all Distribution Groups within an Organization, the following command will do the trick:
Get-DistributionGroup –ResultSize Unlimited | Set-DistributionGroup –ForceUpgrade
While the commands above appear to “upgrade” Distribution Lists from Exchange 2003 to Exchange 2010, I can’t find any Microsoft documentation explaining why this should be necessary. I surmise that simply touching a Distribution Group using an Exchange 2010 Administrative Tool (whether it’s the Console or the Management Shell) may update or add an attribute to the object making it fully functional within Exchange 2010. If anybody has additional information please feel free to leave a comment and share.