Office 365: Why do my distribution group names change?

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I recently worked with a customer that was utilizing directory synchronization to create distribution groups in their on-premises active directory and have them mail enabled within Office 365.  They noticed that when creating these distribution groups the display name in Office 365 was automatically changed and differed from the display name set on-premises.

 

Let’s take a look…

 

Using Active Directory Users and Computers a new distribution list is created.

 

image

 

Using the attribute editor the following attributes were manually set:

 

DisplayName:  TestDL

ProxyAddresses:  SMTP:TestDL@domain.com

Mail:  TestDL@Domain.com

 

After the distribution list was created directory synchronization was performed.  Monitoring directory synchronization we can validate the properties of the group synchronized into Office 365.

 

image

 

Using Powershell connected to Office 365 we can validate the properties of the MSOL Group.

 

PS C:\Users\timmcmic> Get-MsolGroup -ObjectId df617972-c874-4d6d-ba73-993e73219514 | fl

ExtensionData : System.Runtime.Serialization.ExtensionDataObject
CommonName : TestDL
Description :
DisplayName : TestDL
EmailAddress : TestDL@domain.com
Errors : {}
GroupType : DistributionList
IsSystem : False
LastDirSyncTime : 4/9/2014 2:56:34 PM
ManagedBy :
ObjectId : df617972-c874-4d6d-ba73-993e73219514
ProxyAddresses : {smtp:TestDL@domain.onmicrosoft.com, SMTP:TestDL@domain.com}
ValidationStatus : Healthy

 

The attributes of the group within Office 365 and the on-premises Active Directory match after directory synchronization has completed.

 

When reviewing the properties of the same distribution list from Office 365 Exchange it is noted that the name has changed.  In this case a prefix was appended DL_:

 

PS C:\Users\timmcmic> Get-DistributionGroup TestDL | fl NAME,DISPLAYNAME,EMAILADDRESSES

Name : DL_TestDL
DisplayName : DL_TestDL
EmailAddresses : {SMTP:TestDL@domain.com, smtp:TestDL@domain.onmicrosoft.com}

Where did the DL_ come from?  Exchange and Office 365 allow administrators to define a distribution group naming policy.  The distribution group naming policy is set in the organization’s configuration.  More information on distribution group naming policies can be found here:  https://aka.ms/Bry5y2

 

In this instance the tenant had a distribution group naming policy that utilized DL_<GroupName>:

 

PS C:\Users\timmcmic> Get-OrganizationConfig | fl distributiongroupnamingpolicy

DistributionGroupNamingPolicy : DL_<GroupName>

 

When a distribution group naming policy is utilized after directory synchronization has successfully synchronized the group and the new group is provisioned within Exchange Office 365 the naming policy will be applied.  The MSOL object will continue to reflect the attributes as synchronized from the on-premises Active Directory but the Exchange object will reflect the attributes modified by the naming policy.

 

In our case it was desired that the naming policy would not be applied.  This required removing the naming policy from the organizational configuration:

 

PS C:\Users\timmcmic> Set-OrganizationConfig -DistributionGroupNamingPolicy:$NULL

 

By removing the naming policy the Exchange Office 365 groups will now reflect the attributes as synchronized from the on-premises Active Directory.