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.
As of April 2022, DDGs now perform differently than before. Review the changes in the table below:
Use the new EAC to create a dynamic distribution group.
Important
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. |
Important
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.
Important
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.
Note
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.
Use the classic EAC to create a dynamic distribution group.
Important
It can take up to 2 hours for the initial membership list to be calculated and be available for use.
In the Classic EAC, navigate to Recipients > Groups > New > Dynamic distribution group.
On the New dynamic distribution group page, complete the following boxes:
- Display name: Use this box to type the display name. This name appears in the shared address book, on the To: line when email is sent to this group, and in the Groups list in the Classic EAC. The display name is required and should be user-friendly so people recognize what it is. It also must be unique in the forest.
Note
Group naming policy isn't applied to dynamic distribution groups.
Alias: Use this box to type the name of the alias for the group. The alias can't exceed 64 characters and must be unique in the forest. When a user types the alias in the To: line of an email message, it resolves to the group's display name.
Description: Use this box to describe the group so people know what the purpose of the group is. This description appears in the shared address book.
Organizational unit: You can select an organizational unit (OU) other than the default (which is the recipient scope). If the recipient scope is set to the forest, the default value is set to the Users container in the Active Directory domain that contains the computer on which the Classic EAC is running. If the recipient scope is set to a specific domain, the Users container in that domain is selected by default. If the recipient scope is set to a specific OU, that OU is selected by default.
To select a different OU, select Browse. The dialog box displays all OUs in the forest that are within the specified scope. Select the OU you want, and then select OK.
- Owner: An owner for a dynamic distribution group is optional. You can add owners by clicking Browse and then selecting users from the 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.
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.
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 Add a rule to define the criteria for membership in this group.
Select one of the following recipient attributes from the drop-down list and provide a value. If the value for the selected attribute matches that value you define, the recipient receives a message sent to this group.
| Attribute |
Send message to a recipient if... |
| Recipient container |
The recipient object resides in the specified domain or OU. |
| 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. |
Important
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.
In the Specify words or phrases window, type the value in the text box. Select Add and then select OK.
To add another rule to define the criteria for membership, select Add a rule under the previous rule that you created.
Important
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.
When you've finished, select Save to create the dynamic distribution group.
Note
If you want to specify rules for attributes other than the ones available in the Classic 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.
Use Exchange online PowerShell to create a dynamic distribution group.
Important
It can take up to 2 hours for the initial membership list to be calculated and be available for use.
This example creates the dynamic distribution group "Mailbox Users DDG" that contains only mailbox users.
New-DynamicDistributionGroup -IncludedRecipients MailboxUsers -Name "Mailbox Users DDG" -OrganizationalUnit Users
This example creates a dynamic distribution group with a custom recipient filter. The dynamic distribution group contains all mailbox users on a server called Server1.
New-DynamicDistributionGroup -Name "Mailbox Users on Server1" -OrganizationalUnit Users -RecipientFilter "(RecipientTypeDetails -eq 'UserMailbox') -and (ServerName -eq 'Server1')"
This example creates a dynamic distribution group with a custom recipient filter. The dynamic distribution group contains all mailbox users that have a value of "FullTimeEmployee" in the CustomAttribute10 property.
New-DynamicDistributionGroup -Name "Full Time Employees" -RecipientFilter "(RecipientTypeDetails -eq 'UserMailbox') -and (CustomAttribute10 -eq 'FullTimeEmployee')"
For detailed syntax and parameter information, see New-DynamicDistributionGroup.
How do you know this worked?
To verify that you've successfully created a dynamic distribution group, do one of the following:
In the new EAC, navigate to Recipients > Groups. The new dynamic distribution group is displayed in the group list. Under Type, the type is Dynamic distribution group.
In the Classic EAC, navigate to Recipients > Groups. The new dynamic distribution group is displayed in the group list. Under Group Type, the type is Dynamic distribution group.
In Exchange Online PowerShell, run the following command to display information about the new dynamic distribution group.
Get-DynamicDistributionGroup | Format-List Name,RecipientTypeDetails,RecipientFilter,PrimarySmtpAddress
Change dynamic distribution group properties
You can change the group properties, here's how.
In the new EAC, navigate to Recipients > Groups > Dynamic distribution list.
In the list of groups, select the dynamic distribution group that you want to view or change.
On the group's properties page, select one of the following sections to view or change properties.
General
Use this section to view or change basic information about the group.
Name: This name appears in the address book, on the To: line when email is sent to this group, and in the Groups list. The display name is required and should be user-friendly so people recognize what it is. It also has to be unique in your domain.
Description: Use this box to describe the group so people know what the purpose of the group is. This description appears in the address book and in the Details pane in the new EAC.
Email options in new EAC
Use this section to view or change the email addresses associated with the group. This includes the group's primary SMTP addresses and any associated proxy addresses. Under Edit email addresses page, change/edit the Primary email address, add/delete Aliases and then select Save changes.
You can also select the group and then select Edit email addresses from the toolbar to change/edit the Primary email address, add/delete Aliases and then select Save changes.
Members
Use this section to change/edit the following:
Under Owners section, select View all and manage owners to add/remove group owners from the drop-down list and then select Save changes. The dynamic distribution group must have at least one owner.
Use Members section to change the criteria used to determine membership of the group. You can delete or change existing membership rules and add new rules. For procedures that tell you how to do this, see Create a dynamic distribution group
Important
It can take up to 2 hours for the membership list to be recalculated and links updated.
Settings
Under General settings section, select the checkbox Hide from my organization's global address list if you want to hide the group from the list.
Delivery management
Use this section to manage who can send email to this group.
Sender options
By default, only people inside your organization can send message to this group. You can also allow people outside the organization to send to this group.
Only allow messages from people inside my organization: Select this option to allow only senders in your organization to send messages to the group. This means that if someone outside your organization sends an email message to this group, it is rejected. This is the default setting.
Allow messages from people inside and outside my organization: Select this option to allow anyone to send messages to the group.
Specified senders
You can further limit who can send messages to the group by allowing only specific senders to send messages to this group. Select/remove one or more recipients/group from the drop-down list. If you add senders to this list, they're the only ones who can send mail to the group. Mail sent by anyone not in the list will be rejected.
Important
If you've configured the group to allow only senders inside your organization to send messages to the group, email sent from a mail contact is rejected, even if they're added to this list.
Manage delegates
Use this section to assign permissions to a user (called a delegate) to allow them to send messages as the group or send messages on behalf of the group. You can assign the following permissions:
Send As: This permission allows the delegate to send messages as the group. After this permission is assigned, the delegate has the option to add the group to the From line to indicate that the message was sent by the group.
Send on Behalf: This permission also allows a delegate to send messages on behalf of the group. After this permission is assigned, the delegate has the option to add the group on the From line. The message will appear to be sent by the group and will say that it was sent by the delegate on behalf of the group.
To assign permissions to delegates in new EAC, add the delegates under the Edit delegates page, select the Permission type from the drop-down list and select Save changes.
Message approval
Use this section to set options for moderating the group. Moderators approve or reject messages sent to the group before they reach the group members.
Require moderator approval for messages sent to this group: This check box isn't selected by default. If you select this check box, incoming messages are reviewed by the group moderators before delivery. Group moderators can approve or reject incoming messages.
Group moderators: To add/remove group moderators, search/add users from the drop-down list. If you've selected Require moderator approval for messages sent to this group and you don't select a moderator, messages to the group are sent to the group owners for approval.
Add senders who don't require message approval: To add/remove users that can bypass moderation for this group, search/add users from the drop-down list.
Notify a sender if their message isn't approved:: Use this section to set how users are notified about message approval.
Only sender: This is the default setting. Notify all senders, inside and outside your organization, when their message isn't approved.
Only senders in your organization: When you select this option, only users or groups in your organization are notified when a message that they sent to the group isn't approved by a moderator.
No notifications: When you select this option, notifications aren't sent to senders whose messages aren't approved by the group moderators.
How do you know this worked?
To verify that you've successfully changed properties for a dynamic distribution group:
- Select the group to view the property or feature that you changed. Depending on the property that you changed, it might be displayed in the details pane for the selected group.
In the Classic EAC, navigate to Recipients > Groups.
In the list of groups, select the dynamic distribution group that you want to view or change, and then select Edit 
.
On the group's properties page, select one of the following sections to view or change properties.
General
Use this section to view or change basic information about the group.
Display name: This name appears in the address book, on the To: line when email is sent to this group, and in the Groups list. The display name is required and should be user-friendly so people recognize what it is. It also has to be unique in your domain.
Alias: This is the portion of the email address that appears to the left of the at (@) symbol. If you change the alias, the primary SMTP address for the group will also be changed, and contain the new alias. Also, the email address with the previous alias will be kept as a proxy address for the group.
Description: Use this box to describe the group so people know what the purpose of the group is. This description appears in the address book and in the Details pane in the Classic EAC.
Hide this group from address lists: Select this check box if you don't want users to see this group in the address book. To send email to this group, a sender has to type the group's alias or email address on the To: or Cc: lines.
Organizational unit: This read-only box displays the organizational unit (OU) that contains the dynamic distribution group. You have to use Active Directory Users and Computers to move the group to a different OU.
Ownership
Use this section to assign a group owner. A dynamic distribution group can have only one owner. The group owner appears on the Managed by tab of the object in Active Directory Users and Computers.
You can add owners by clicking Browse and selecting the owner from the list. To remove the owner, select Clear and then select Save.
.
Membership
Use this section to change the criteria used to determine membership of the group. You can delete or change existing membership rules and add new rules. To learn how, see Create a dynamic distribution group.
Delivery management
Use this section to manage who can send email to this group.
Only senders inside my organization: Select this option to allow only senders in your organization to send messages to the group. This means that if someone outside your organization sends an email message to this group, it is rejected. This is the default setting.
Senders inside and outside of my organization: Select this option to allow anyone to send messages to the group.
You can further limit who can send messages to the group by allowing only specific senders to send messages to this group. Select Add 
and then select one or more recipients. If you add senders to this list, they're the only ones who can send mail to the group. Mail sent by anyone not in the list will be rejected.
To remove a person or a group from the list, select them in the list and then select Remove .
Important
If you've configured the group to allow only senders inside your organization to send messages to the group, email sent from a mail contact is rejected, even if they're added to this list.
Message approval for membership
Use this section to set options for moderating the group. Moderators approve or reject messages sent to the group before they reach the group members.
Messages sent to this group have to be approved by a moderator: This check box isn't selected by default. If you select this check box, incoming messages are reviewed by the group moderators before delivery. Group moderators can approve or reject incoming messages.
Group moderators: To add group moderators, select Add . To remove a moderator, select the moderator, and then select Remove . If you've selected "Messages sent to this group have to be approved by a moderator" and you don't select a moderator, messages to the group are sent to the group owners for approval.
Senders who don't require message approval: To add people or groups that can bypass moderation for this group, select Add . To remove a person or a group, select the item, and then select Remove .
Select moderation notifications: Use this section to set how users are notified about message approval.
Notify all senders when their messages aren't approved: This is the default setting. Notify all senders, inside and outside your organization, when their message isn't approved.
Notify senders in your organization only when their messages aren't approved: When you select this option, only people or groups in your organization are notified when a message that they sent to the group isn't approved by a moderator.
Don't notify anyone when a message isn't approved: When you select this option, notifications aren't sent to senders whose messages aren't approved by the group moderators.
Email options
Use this section to view or change the email addresses associated with the group. This includes the group's primary SMTP addresses and any associated proxy addresses. The primary SMTP address (also known as the reply address) is displayed in bold text in the address list, with the uppercase SMTP value in the Type column.
Add: Select Add to add a new email address for this mailbox. Select one of following address types:
SMTP: This is the default address type. Select this button and then type the new SMTP address in the * Email address box.
Note
To make the new address the primary SMTP address for the group, select the Make this the reply address check box.
Custom address type: Select this button and type one of the supported non-SMTP email address types in the * Email address box.
Note
With the exception of X.400 addresses, Exchange doesn't validate custom addresses for proper formatting. You must make sure that the custom address you specify complies with the format requirements for that address type.
Edit: To change an email address associated with the group, select it from the list, and then select Edit .
Note
To make an existing address the primary SMTP address for the group, select the Make this the reply address check box.
Remove: To delete an email address associated with the group, select it from the list, and then select Remove .
Automatically update email addresses based on the email address policy applied to this recipient: Select this check box to have the recipient's email addresses automatically updated based on changes made to email address policies in your organization. This box is selected by default.
MailTip
Use this section to add a MailTip to alert users of potential issues before they send a message to this group. A MailTip is text that's displayed in the InfoBar when this group is added to the To, Cc, or Bcc lines of a new email message. For example, you could add a MailTip to large groups to warn potential senders that their message will be sent to lots of people.
Note
MailTips can include HTML tags, but scripts aren't allowed. The length of a custom MailTip can't exceed 175 displayed characters. HTML tags aren't counted in the limit.
Group delegation
Use this section to assign permissions to a user (called a delegate) to allow them to send messages as the group or send messages on behalf of the group. You can assign the following permissions:
Send As: This permission allows the delegate to send messages as the group. After this permission is assigned, the delegate has the option to add the group to the From line to indicate that the message was sent by the group.
Send on Behalf Of: This permission also allows a delegate to send messages on behalf of the group. After this permission is assigned, the delegate has the option to add the group on the From line. The message will appear to be sent by the group and will say that it was sent by the delegate on behalf of the group.
To assign permissions to delegates in Classic EAC, select Add under the appropriate permission to display the Select Recipient page, which displays a list of all recipients in your Exchange organization that can be assigned the permission. Select the recipients you want, add them to the list, and then select OK. You can also search for a specific recipient by typing the recipient's name in the search box and then clicking Search.
How do you know this worked?
To verify that you've successfully changed properties:
- Select the group and then select Edit to view the property or feature that you changed. Depending on the property that you changed, it might be displayed in the details pane for the selected group.
Use the Get-DynamicDistributionGroup and Set-DynamicDistributionGroup cmdlets to view and change properties for dynamic distribution groups. Advantages of using Exchange Online PowerShell are the ability to change the properties that aren't available in the EAC and change properties for multiple groups. For information about what parameters correspond to distribution group properties, see the following articles:
Here are some examples of using Exchange Online PowerShell to change dynamic distribution group properties.
This example changes the following parameters for all dynamic distribution groups in the organization:
Hide all dynamic distribution groups from the address book
Set the maximum message size that can be sent to the group to 5 MB
Enable moderation
Assign the administrator as the group moderator
Get-DynamicDistributionGroup -ResultSize unlimited | Set-DynamicDistributionGroup -HiddenFromAddressListsEnabled $true -MaxReceiveSize 5MB -ModerationEnabled $true -ModeratedBy administrator
This example adds the proxy SMTP email address, Seattle.Employees@contoso.com, to the All Employees group.
Set-DynamicDistributionGroup -Identity "All Employees" -EmailAddresses SMTP:All.Employees@contoso.com, smtp:Seattle.Employees@contoso.com
Important
It can take up to 2 hours for the membership list to be recalculated and links updated.
How do you know this worked?
To verify that you've successfully changed properties:
Use the Get-DynamicDistributionGroup cmdlet to verify the changes. One advantage of using Exchange Online PowerShell is that you can view multiple properties for multiple groups. In the first example, you would run the following command to verify the new values.
Get-DynamicDistributionGroup -ResultSize unlimited | Format-List Name,HiddenFromAddressListsEnabled,MaxReceiveSize,ModerationEnabled,ModeratedBy
For the example above where the message limits were changed, run this command.
Get-Mailbox -OrganizationalUnit "Marketing" | Format-List Name,IssueWarningQuota,ProhibitSendQuota,ProhibitSendReceiveQuota,UseDatabaseQuotaDefaults
Using DDGs in a government cloud
If your tenant resides in a government cloud, including GCC, GCC High, or DoD, the Dynamic Distribution Groups, DDGs function differently.
For government clouds, the membership list for dynamic distribution groups is calculated each time a message is sent to the group, based on the filters and conditions that you define. When an email message is sent to a dynamic distribution group, it's delivered to all recipients in the organization that match the criteria defined for that group.
View group members (Government cloud only)
Use Exchange Online PowerShell to preview the list of members of a dynamic distribution group
This example returns the list of members for the dynamic distribution group named Full Time Employees.
$FTE = Get-DynamicDistributionGroup "Full Time Employees"
Get-Recipient -RecipientPreviewFilter $FTE.RecipientFilter -OrganizationalUnit $FTE.RecipientContainer
This example displays the list of users and email addresses for the same group if it has more than 1,000 members.
$FTE = Get-DynamicDistributionGroup "Full Time Employees"
Get-Recipient -ResultSize Unlimited -RecipientPreviewFilter $FTE.RecipientFilter -OrganizationalUnit $FTE.RecipientContainer | Format-Table Name,Primary*
For detailed syntax and parameter information, see Get-DynamicDistributionGroupMember.
How do you know this worked?
To verify that you've successfully viewed the members of a dynamic distribution group, run Get-DynamicDistributionGroupMember to view the list of group members. For example, if you created a new user mailbox with properties that match the recipient filter for the dynamic distribution group, this new mailbox should be displayed in the list of group members.