Manage dynamic distribution groups in Exchange Online
A new version of this feature is currently being rolled out to customers. Modern Dynamic Distribution Groups will be fully released by April 2022, replacing the earlier method.
Dynamic distribution groups (DDGs) are mail-enabled Active Directory group objects that are created to expedite the mass sending of email messages and other information within a Microsoft Exchange organization.
DDGs in Exchange Online have been modernized to bring a more reliable, predictable, and better performing experience. This change will reduce mail delivery latency, improve service reliability, and allow you to see the members of a DDG before sending a message.
The membership list is now stored for each DDG and is updated once every 24 hours. You'll know exactly to whom the message is being sent, and it also addresses potential compliance issues. By storing the calculated list of members on the DDG object, messages can be delivered more quickly and our service will have greater reliability.
Government cloud: If your tenant resides in a government cloud, including GCC, GCC High, or DoD, Dynamic Distribution Groups function differently.
To learn more, see Using Dynamic Distribution groups in a government cloud
Important changes in DDGs
As of April 2022, DDGs now perform differently than before. Review the changes in the table below:
|Area||Old behavior||New behavior|
|Mail delivery latency||Unpredictable. The time it takes to deliver mail to a DDG depends on how complex the filters are on that DDG.||Faster and more predictable overall. You should see delivery times more in line with those for regular distribution groups.|
|Creation||DDGs could be used immediately after being created.||It takes 2 hours for the initial membership list to be calculated and be available for use.|
|Modification||DDGs could be used immediately after any changes were made||Users have to wait up to 2 hours for the membership list to be recalculated and links updated.|
|Membership list "freshness"||The list of members was up to date in real time.||The list of members for each DDG is refreshed every 24 hours.|
- The list of DDG members might become stale. For example, if a user has left a department that was used as a filter for the DDG, they might continue to receive mail that's sent to the DDG for the next 24 hours util the membership list is refreshed.
- Mail flow rules (also known as transport rules) are also affected by this behavior, because the membership list that the mail flow rules use is also refreshed once every 24 hours.
- A dynamic distribution group includes any recipient in Active Directory with attribute values that match its filter. If a recipient's properties are modified to match the filter, the recipient could inadvertently become a group member and start receiving messages that are sent to the group. Well-defined, consistent account provisioning processes will reduce the chances of this issue occurring.
- Dynamic distribution groups are not synced from Exchange Online to Microsoft Entra ID or to your on-premises Active Directory. Therefore, features such as Azure Conditional Access do not support being scoped to an Exchange Online dynamic distribution group.
Before you begin
You need to be assigned permissions before you can perform this procedure or procedures. To see what permissions you need, see the "Recipients" entry in the Feature permissions in Exchange Online article.
For information about keyboard shortcuts that may apply to the procedures in this article, see Keyboard shortcuts for the Exchange admin center.
Create a dynamic distribution group
- In the new EAC
- In the Classic EAC
- With Exchange Online PowerShell
- With new EAC
- With the classic EAC
- With Exchange Online PowerShell
Use the new EAC to create a dynamic distribution group.
It can take up to 2 hours for the initial membership list to be calculated and be available for use.
In the new EAC, navigate to Recipients > Groups.
Select Add a group and follow the instructions in the details pane.
Under Choose a group type section, select Dynamic distribution group and select Next.
Under Set up the basics section, enter the details and select Next.
In Assign Users section, select the group owner from the drop-down list.
Use the Members section to specify the types of recipients for the group and set up rules that will determine membership. Select one of the following boxes:
All recipient types: Choose this option to send messages that meet the criteria defined for this group to all recipient types.
Only the following recipient types: Messages that meet the criteria defined for this group will be sent to one or more of the following recipient types:
Users with Exchange mailboxes: Select this check box if you want to include users that have Exchange mailboxes. Users that have Exchange mailboxes are those that have a user domain account and a mailbox in the Exchange organization. Resource mailboxes are also included.
Mail users with external email addresses: Select this check box if you want to include users that have external email addresses. Users that have external email accounts have user domain accounts in Active Directory, but use email accounts that are external to the organization. This enables them to be included in the global address list (GAL) and added to distribution lists.
Resource mailboxes: Select this check box if you want to include Exchange resource mailboxes. Resource mailboxes allow you to administer company resources through a mailbox, such as a conference room or a company vehicle.
Mail contacts with external email addresses: Select this check box if you want to include contacts that have external email addresses. Contacts that have external email addresses don't have user domain accounts in Active Directory, but the external email address is available in the GAL.
Mail-enabled groups: Select this check box if you want to include security groups or distribution groups that have been mail-enabled. Mail-enabled groups are similar to distribution groups. Email messages that are sent to a mail-enabled group account will be delivered to several recipients.
Select one of the following attributes from the drop-down list and provide a value to define the criteria for membership in this group.
Attribute Send message to a recipient if... State or province The specified value matches the recipient's State or province property. Company The specified value matches the recipient's Company property. Department The specified value matches the recipient's Department property. Custom attribute N (where N is a number from 1 to 15) The specified value matches the recipient's CustomAttributeN property.
The values that you enter for the selected attribute must exactly match those that appear in the recipient's properties. For example, if you enter Washington for State or province, but the value for the recipient's property is WA, the condition will not be met. Also, text-based values that you specify aren't case-sensitive. For example, if you specify Contoso for the Company attribute, messages will be sent to a recipient if this value is contoso.
To add another rule to define the criteria for membership, select Add another rule, when you've finished, select Next.
If you add multiple rules to define membership, a recipient must meet the criteria of each rule to receive a message sent to the group. In other words, each rule is connected with the Boolean operator AND.
In Edit settings section, enter the group email address and select Next.
In Review and finish adding group section, verify all the details, select Create group and then select Close.
If you want to specify rules for attributes other than the ones available in the new EAC, you must use Exchange Online PowerShell to create a dynamic distribution group. Keep in mind that the filter and condition settings for dynamic distribution groups that have custom recipient filters can be managed only by using Exchange Online PowerShell. For an example of how to create a dynamic distribution group with a custom query, see the next section on using Exchange Online PowerShell to create a dynamic distribution group.