How to Create Dynamic Distribution Groups in Microsoft 365

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Dynamic Distribution Group (DDG) is one of the recipient types available in on-premises Microsoft Exchange Server 2019, 2016. A Dynamic Distribution Group is a type of mail group in which membership is automatically determined based on filters and conditions, such as department, location, or other user attributes in Active Directory. The list of members is generated in real time when an email is sent to the group. Email sent to the group SMTP address is automatically resent to all members.

Keep in mind that Dynamic Distribution Groups calculate membership when a message is sent and do not maintain a static member list. They cannot be used for assigning permissions/Microsoft Teams membership.

Creating and managing DDLs and recipient filters in Exchange Server 2019

Let’s look at how to create and manage DDLs and their recipient filters in Exchange Server 2019.

To manage a dynamic distribution group, you can use the Exchange Admin Center (EAC) web interface. Let’s create a simple dynamic group that includes all users in the IT department.

1. Sign-in EAC.
2. Navigate to recipients > groups > click + and select Dynamic distribution group.
   

   

3. Specify the name of the new group and the Active Directory OU in which to create it.
   

   

4. Scroll down the group properties form.
   Here, you can choose which types of recipients will be included as members of the group: all, user/resource mailboxes, mail contacts, or mail-enabled groups.
5. In this case we have selected the Users with Exchange mailbox option.

   

6. Next, in the membership settings, define the rules that will automatically add users to the group.
7. Click Add a rule.
8. Recipient container, state, company, department and 15 custom attributes are available in the ECP web interface.
9. We selected Department (with the value IT) and specified the Recipient container (the Organizational Unit in AD from which users should be added to the dynamic group).
   

   

10. Click OK to create a new group.

All user mailboxes from the selected OU whose Department property is set to IT will be included in the dynamic distribution group we have created. Now, if a user is transferred to another department and the value of this attribute in AD changes, they will be automatically removed from this distribution list.

Checking if the filter is working correctly

How to check that the filter is working correctly and see which users are included in the DDG group? You cannot view the members of a dynamic group in ECP or in the Outlook address list.

Use PowerShell (Exchange Management Shell) to list the dynamic group members:

Get-Recipient -RecipientPreviewFilter (Get-DynamicDistributionGroup -Identity hq-admins).RecipientFilter| select Name, RecipientType, PrimarySmtpAddress

The current settings of the DDG filter can be viewed using the following command:

Get-DynamicDistributionGroup hq-admins| fl name,*filter*,*container

Membership of a dynamic group is calculated each time the message is sent to a group.

How to create and manage dynamic distribution groups in Exchange Server using PowerShell

Creating and managing filters in DDG is much more flexible with PowerShell. For example, only about 20 user attributes that can be used as group filters are available in the ECP Web UI. You can check the complete list of filterable properties for RecipientFilter parameter in Exchange Server.

Let’s look at some typical PowerShell commands for creating and managing dynamic distribution groups in Exchange Server.

Create a new dynamic group

Create a new dynamic group of all users whose Company field is TheITBros and whose City field is Houston;

New-DynamicDistributionGroup `

-Name "Houston TheITBros Team" `

-Alias "HOU-TheITBros" `

-RecipientContainer "theitbros.com/Houston/Groups" `

-RecipientFilter "((Company -eq 'TheITBros') -and (City -eq 'Houston'))"

After that, you need to verify that the new dynamic distribution group has been created successfully:

Get-DynamicDistributionGroup "Houston TheITBros Team"

In order to list all dynamic distribution groups, run the command:

Get-DynamicDistributionGroup |
Select-Object Name, PrimarySmtpAddress

Here is an example of a more advanced recipient filter:

New-DynamicDistributionGroup `
-Name "London IT Users" `
-Alias "LondonITUsers" `
-RecipientFilter "((RecipientTypeDetails -eq 'UserMailbox') -and (Department -eq 'IT') -and (Office -eq 'London'))"

Change the DDG settings with Set-DynamicDistributionGroup

Use the Set-DynamicDistributionGroup cmdlet to change the DDG settings. In this example, we will exclude a specific user (by SMTP address) from this dynamic group:

Set-DynamicDistributionGroup -Identity "Houston TheITBros Team" -RecipientFilter "((Company -eq 'TheITBros') -and (City -eq 'Houston') -and (PrimarySmtpAddress -ne 'v.ebner@theitbros.com'))"

Note that you cannot change the membership rule of a dynamic distribution group created using PowerShell from the ECP web interface.

This dynamic distribution group was created by using the Exchange Management Shell. Use the Shell to change the filter.

In order to remove a dynamic distribution group, use the following command:

Remove-DynamicDistributionGroup "Houston TheITBros Team"

Creating a Dynamic Distribution Group in Exchange Online

Before running Exchange Online cmdlets, you need to connect to Exchange Online PowerShell with the command:

Connect-ExchangeOnline

Then you need to create a dynamic distribution group. Use the following command:

New-DynamicDistributionGroup `
-Name "Sales Team" `
-Alias "SalesTeam" `
-RecipientFilter "(Department -eq 'Sales')"

The example mentioned above creates a dynamic distribution group that automatically includes all mailboxes where the Department attribute is set to Sales.

Wrapping up

Dynamic groups in Exchange Server are a powerful and convenient tool for managing distribution lists within an organization. DDGs are supported in both Exchange Server and Exchange Online. In Exchange Online, they are managed through Exchange Online PowerShell and Exchange Admin Center using recipient filters.