Microsoft 365 and Office | Install, redeem, activate | For business | Other
Processes in Microsoft 365 for setting up Office apps, redeeming product keys, and activating licenses.
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Hi @Federico Ciampi,
Thank you so much for sharing such a detailed and well-researched question. I'm happy to answer based on my understanding of the Exchange Online behavior and the information currently documented by Microsoft.
1/Is it by design that a Microsoft 365 Group cannot be used as an authorized sender on a Dynamic Distribution List?
Yes, this is by design. For the AcceptMessagesOnlyFromSendersOrMembers parameter, the supported values are:
- Individual senders: mailboxes, mail users, and mail contacts.
- Groups: distribution groups, mail-enabled security groups, and dynamic distribution groups.
A Microsoft 365 Group, also known as a Unified Group, is not included in the supported group types. Therefore, it will not appear as a valid selection under Delivery management > Specified senders.
2/ Is there any supported way (UI or PowerShell via Set-DynamicDistributionGroup) to make it work with a Microsoft 365 Group directly?
At this time, I am not aware of any supported method to use a Microsoft 365 (Unified) Group directly as an authorized sender for a Dynamic Distribution Group.
While Set-DynamicDistributionGroup does expose the AcceptMessagesOnlyFromSendersOrMembers parameter, Microsoft documentation does not identify Unified Groups as a supported object type for this setting. Additionally, the fact that the Microsoft 365 Group cannot be selected in the Exchange admin center is consistent with that limitation and suggests that this scenario is not currently supported.
3/If not, is a mail-enabled security group mirroring the M365 Group membership the recommended approach?
Yes. In my opinion, a mail-enabled security group would be the most practical and fully supported workaround in this scenario. A standard distribution group could also be used if security-based permissions are not required.
You can add the users who should have sending rights to the mail-enabled security group and then configure that group as an authorized sender under the Dynamic Distribution List's Specified senders setting. When a supported group is granted permission, all members of that group are allowed to send messages to the Dynamic Distribution List.
Please note that Exchange Online does not automatically synchronize membership between a Microsoft 365 Group and a separate mail-enabled security group. The membership must therefore be maintained manually or synchronized through administrative automation. If only a small number of users require permission, you may alternatively add their individual mailboxes directly rather than maintaining another group.
I sincerely appreciate your time in reviewing the information I've shared and your willingness to consider the available options!
Thank you again for bringing this question to the community. I hope the explanation helps clarify the current behavior and provides a useful direction for your implementation and future reference.
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