Microsoft is encouraging customers to adopt Office 365 Groups more and more instead of using simple distribution lists. So much so that when you try to create a DL in Office 365 Exchange admin, the UI to create an Office 365 Group pops-up first :-) ..and from there you can navigate to the UI to create a simple DL.
The distribution lists in Office 365 tenant can be migrated to Office 365 Groups. This can be done either through the Exchange admin center UI or through Powershell scripts.
Through User interface :
From the Exchange admin, select the Distribution list from Groups and click the “Migrate to Office 365 groups” button
This will upgrade the disctribution list or it will show an error if the DL is not eligible to be migrated.
Eligibility critera :
Not all types of Distribution lists can be migrated to Office 365 Groups. Here is the documentation that explains what type of DLs are eligible and not eligible for upgrade.
Old documentation ?
At the time of writing this, the documentation in the above posted link mentions that the Moderated DLs and DLs with send on behalf setting cannot be upgraded, however I found this inconsistent. These two types of DLs CAN be upgraded and looks like the documentation is not updated (?)
I posted a query on tech community forum and from the response I gathered that the documentation will be updated soon
Here is the forum post : https://techcommunity.microsoft.com/t5/Office-365-Groups/Upgrade-Distribution-list-to-O-365-group-criteria-not-enforced/m-p/61344
I will try and update this post as and when I find that the documentation on Office support site is updated.
PowerShell approach :
Microsoft has provided Powershell scripts that evaluate the distribution lists in your tenant and provide a report of eligibilty as to whether the DLs can be migrated to Office 365 Groups or not
I decided to do an evaluation considering a couple of scenarios. From exchange online I created 6 distribution list each satisfying the below criterias
- DL with send on behalf setting
- Moderated DL
- Simple DL with users
- DL with external contacts : Mail user and mail contact
- Nested Parent-Child DLs
The scripts are available to be downloaded from the Microsoft documentation, You need to connect to the Exchange online in your tenant and then execute the script. On executing the Get-DlEligibilityList.ps1 two files are generated - Open the output files in excel (though these are TXT files)
DlEligibilityList.txt : This file lists all the DLs and whether it is eligible to be upgraded or not along with reasons and some other useful information such as
- Owner of the DL
- Member count
- Reasons if the DL is not eligible.
Again, as specified in earlier above section, the DLs with send as behalf and moderated DLs are eligible and CAN be migrated.
MailUniversalDistributionList.txt : This file contains the properties/settings of the Distribution list and indicates whether the DL is nested in some other DL or not
What happens to the Distribution lists with external “Mail user” or “Mail Contact”
I have a added few external email IDs as Mail user and Mail contact in Exchange online. I created two Distribution lists, one having a Mail user and one having Mail contact.
When you try to upgrade a distribution list with a Mail contact, it fails with the following error as indicated by the the eligibility report.
When you try to upgrade a distribution list with a Mail user, it upgrades successfully. The external mail user is added as a member to the new Office 365 Group.