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Two Interesting Features Coming Soon to Exchange Online
Last week, the Exchange Online development group announced two interesting product updates. The first is described in message center notification MC1420903 (July 8, 2026) to inform tenants about a new check during the creation process for dynamic distribution groups (DDGs) to prevent the creation of duplicate groups. The second is the introduction of a cross-tenant message recall capability, something that requires administrators to decide what other tenants they will permit to recall messages delivered to their organization.
An Ongoing Effort to Improve Dynamic Distribution Groups
The heart of a DDG is its recipient filter. Exchange Online resolves the filter against its directory (DDGs are not Entra ID objects) to build the recipient list. Exchange Online includes a set of precanned recipient filters, meaning that they are well-known pre-prepared filters like “All mailboxes.” Other recipient filters are expressed in OPATH format to find specific sets of mail-enabled recipients.
Resolving filters to build recipient lists consumes server resources. Over the years, Microsoft has moderated the requirement for server resources by introducing “modern” dynamic distribution groups in early 2022 and by limiting the number of DDGs per tenant to 3,000 in April 2025. They also fixed some bugs in recipient list calculation, notably around wildcard usage for email domains.
In that light, stopping tenants from creating duplicate DDGs is both logical and sensible. I can’t think of a good reason to support duplicate DDGs and with the per-tenant limit of 3,000 DDGs, it doesn’t make sense to allow unnecessary DDGs to occupy slots that could be used by more valuable groups.
Implementing the Block for Duplicate Dynamic Distribution Groups
The block applies to creation of dynamic distribution groups through all administrative interfaces, including PowerShell. When creating a new DDG, Exchange Online checks the following properties:
- Recipient filter.
- Delivery management settings.
- Message approval (moderation) settings.
- Delegation settings.
- Message visibility settings.
If the values of all the settings match an existing DDG, Exchange returns an error to say that a matching DDG already exists.
The change is not retrospective and existing DDG continue to work as before. And to answer the inevitable question, Microsoft hasn’t said whether this feature will show up in Exchange Server SE. The need to preserve cloud resources doesn’t exist on premises.
Introducing Cross-Tenant Message Recall
Over three years ago, Microsoft rolled out the vastly improved message recall feature for Exchange Online. Subsequent changes include the ability to recall protected messages, but only for web clients. At the same time, Microsoft added recall message to the Outlook mobile clients. Now they’re addressing a major customer ask by adding support for cross-tenant message recall. According to message center notification MC1423106 (July 10, 2026), general availability should start deployment to all clouds in mid-August 2026 with full deployment scheduled by early-September.
The problem with message recall has always been that although the facility works beautifully for messages sent within a tenant, it could not retrieve email once a message hit a connector and went outside the tenant, even if the message went to another Microsoft 365 tenant.
Given that so much email is sent externally, not being able to recall a message sent in error and delivered externally when the message might contain some information the sender didn’t want to share is a problem. Obviously, confidential email should be protected by sensitivity labels with encryption that restrict access to a specific audience, but accidents do happen.
Microsoft’s solution is to create a cross-tenant message recall trust list (allow list). When someone finds that they need to recall a message, they select the message and use the message recall option (Figure 1). Behind the scenes, Exchange Online recalls messages delivered internally and checks with other tenants if it is possible to recall messages delivered there.
Each tenant decides whether external organizations can request message recall. If tenants enable the recall facility, they must also configure an allow list of external tenants permitted to recall messages. If a tenant that receives a copy of a message allows the sending tenant to recall it, Exchange uses the same process that occurs today for messages recalled inside a tenant. If the receiving tenant doesn’t permit external recall or the sending tenant isn’t in the allow list, the recall attempt fails, just like it would do today. No client updates are necessary because everything is processed by the service.
No solution is available for messages delivered to non-Microsoft 365 destinations. If someone makes a mistake and sends the company’s confidential thoughts in an unprotected email to a Gmail or Proton Email address, they can do nothing about it.
Configuring Cross-Tenant Message Recall
In a nutshell, the receiving tenant controls how recall works. It does so by configuring whether it wants to enable cross-tenant message recall and setting up an allow list.
To enable cross-tenant message recall, connect to the Exchange Online management module and run:
Set-CrossTenantRecallConfiguration -CrossTenantRecallEnabled $true
To disable the feature, run the cmdlet to set the value to $false. This is also the default value, so there’s no need to do anything unless you want to enable cross-tenant message recall.
To add the tenants your tenant will allow to recall messages, update the tenant recall configuration with the tenant identifiers. This web site is an easy way to find the tenant identifier for an organization:
Set-CrossTenantRecallConfiguration -AllowedSenderTenantIds @{Add="91c369b5-1c9e-439c-989c-1867ec606603","72f988bf-86f1-41af-91ab-2d7cd011db47", "22e90715-3da6-4a78-9ec6-b3282389492b"}
If you enable cross-tenant message recall and don’t configure an allow list, no external tenant can recall messages.
The Set-CrossTenantRecallConfiguration cmdlet isn’t currently available in V3.10 of the Exchange Online management module.
Evolutionary Changes but Valuable Nonetheless
Neither of these changes will dramatically change the use of Exchange Online. Removing the ability to create duplicate dynamic distribution groups will probably benefit Microsoft more than tenants, most of whom won’t be near the threshold for DDGs. The real value is in cross-tenant message recall. Its greatest benefit is not avoiding embarrassment after an accidental send, but the ability to retrieve confidential information mistakenly sent to trusted partners in other Microsoft 365 tenants.
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