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When an organization moves from an on-premises platform, such as Exchange, SharePoint and Skype for Business, to Office 365, it's important to analyze existing distribution groups to determine how to migrate to the cloud.
Office 365 Groups is a collaborative service that takes the place of traditional distributions groups. However, administrators must understand how the services differ and use caution when they create Office 365 Groups from the existing distribution groups.
Here are five points an organization should review as it considers what's involved to convert distribution groups into Office 365 Groups.
Study up on Office 365 Groups
When admins create Office 365 Groups, they install a collaboration service that extends across Office 365 services. In addition to email collaboration, Office 365 Groups provides access to shared resources, such as a mailbox, calendar, document library, team site and planner. Office 365 Groups also forms the foundation for other Office 365 services, such as Microsoft Teams.
When new members join Office 365 Groups, they immediately gain access to the conversation history in a dedicated shared mailbox. In a traditional distribution group, new members cannot access previous conversations and only receive messages from the time they join the group.
Analyze groups and determine migration options
An organization with an existing distribution group structure can convert them to Office 365 Groups and maintain some -- or all -- of that arrangement. Admins can extend the functionality further with the additional Office 365 Groups features. Evaluate existing distribution groups to determine if they are in use; this is a good time to eliminate any unwanted or unused groups.
Admins can convert a single distribution group when they create Office 365 Groups with a single click in the Office 365 Exchange Administration Center. Microsoft provides conversion scripts to convert multiple distribution groups to Office 365 Groups. Administrators should evaluate the scripts in a nonproduction environment before they create Office 365 Groups.
Understand the migration eligibility status
Microsoft conversion scripts will not work in all instances. Administrators cannot convert distribution groups to Office 365 Groups if any of the following factors exist:
- They are mastered on premises, such as when synchronized from an on-premises Exchange environment into Office 365 via the Azure Active Directory Connect tool.
- They have Send on Behalf Of permissions set.
- They are configured as a moderated group.
- The distribution group is hidden from the address list.
- They have nested groups or are nested within other groups.
Microsoft's conversion scripts include the Get-DlEligibilityList.ps1 script, which determines a group's migration eligibility status. The script checks all distribution groups in an Office 365 tenant and outputs the eligibility results into a file. The output file will indicate if a distribution group cannot be converted if, for example, it is a closed group. The output file will provide some conversion assistance and show when the administrator can convert a distribution group to an Office 365 Group with an override switch in the conversion script.
Another script, named Convert-DistributionGroupToUnifiedGroup.ps1, uses the output file to perform the conversion.
Hybrid migration obstacles
Microsoft conversion scripts have limits; they cannot convert distribution groups that are mastered on premises in a hybrid configuration to Office 365 Groups.
Microsoft developed a distribution list migration script, named Hummingbird, to help in this scenario. Hummingbird backs up the on-premises distribution group's configuration and creates a new Office 365 Group from membership details in the original distribution group.
However, because the original distribution group syncs with Office 365, the tool must avoid duplicate configuration settings, such as email addresses. Consequently, some of the new Office 365 Group's configuration settings will differ from the original distribution group. Administrators must perform other changes -- remove the original distribution list and update the Office 365 Group to use the original email address -- manually.
While administrators can build their own scripts to tackle this issue, they should test in a nonproduction environment to ensure success.
Assess governance and user self-service
As part of a move to Office 365, organizations must have a clear process to create Office 365 Groups. By default, users can also create Office 365 Groups through different clients or applications, such as Outlook, Outlook on the Web, SharePoint team sites and Planner. Admins can restrict this through a mixture of Outlook Web Access mailbox policies and Azure Active Directory configuration settings. Carefully evaluate whether to control group creation or deploy a user self-service model.
Admins can configure Office 365 Groups for a consistent naming standard. This is important, particularly in hybrid scenarios where groups created in Office 365 are written back to the on-premises environment. Review the naming policies for current distribution groups and new Office 365 Groups accordingly.
Evaluate Office 365 external access limitations
Use ADFS policies to control access to Office 365
Benefits of a hybrid setup with Office 365