In a previous blog post, I wrote about the value of the new Office 365 “Groups.” These are a next generation type of group that replaces the function of a traditional distribution group, and includes the benefits of a security group, along with many other rich collaboration experiences. For example, they offer a shared calendar, shared files via OneDrive, shared OneNote, and a group chat experience in OWA. You can use these groups for Azure AD SSO, and the new March preview of AAD-Connect will dirsync these groups to on-premises.

See: Office 365 “Groups” are next generation distribution lists
and Upgrading Dirsync to Azure Active Directory Connect Public Preview – March 2015 update

I was inspired to write this post after reading my colleague’s post on how to update the primary SMTP address: http://blog.ucparticles.com/2014/11/office-365-groups-how-to-update-primary.html

Basically, when a new “Office 365 Group” is created, it gets stamped with an MyTenant.onmicrosoft.com address, for example: [email protected]

In Keif’s blog post above, he demonstrates how to use Exchange Online remote powershell to update the address to match the vanity domain name, ex: [email protected]. This improves aesthetics and mail routing.

• Obtain a list of existing Office 365 Group mailboxes

  Get-GroupMailbox

• Use the following one-liner to update the primary SMTP address

  Set-GroupMailbox –Identity Name –PrimarySMTPAddress groupname@defaultdomain.com (Insert primary domain here)

Keif also posted a powershell script to read from a CSV file and convert the groups to the new SMTP format. Awesome!

So this solves one part of the conversion, which is to get the groups to use the shorter SMTP domain format.

What about the overall process itself? Let’s say you have 100 distribution groups today and you want to convert them all to Office 365 Groups? How would you go about doing this?

Approach #1 – Create a new O365 Group and then add the existing DL as a ‘member’

Approach #2 – Create a new O365 Group and then delete the old DL. Inform users to start using the new Group.

Approach #3 – Create a new O365 Group, delete the old DL and then update the new O365 Group to use the old DL’s SMTP name, or add it as a secondary proxy alias

There are tradeoffs with each approach, but in general you want to select the approach that prevents NDR’s from occurring, and you want to make sure to automatically subscribe the members of the old DL to the new O365 Group so that they don’t have to manually take any action in order to start receiving new emails from the group. In a future blog post, I will walk through the end to end process.

Update 5/20/2015: If you take approach #3,  I now recommend leaving the primary SMTP address as the onmicrosoft.com address, and adding the old DL as a secondary proxy address. The reason for this is because the new Office 2016 Office Client will not display these Groups if the primary address is not an onmicrosoft.com domain name.