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Multiselection in Outlook web add-in in Outlook Web/New Outlook with Unified manifest

Andjela Mijailovic 20 Reputation points
2026-03-06T14:07:20.0433333+00:00

Hello,

We migrated our solution from a COM add-in to an Outlook Web Add-in (Office.js).

As part of this transition, we also encouraged our clients to move to the new Outlook.

Our add-in uses the Unified Manifest model.

We are now trying to implement functionality that depends on selecting multiple emails. However, based on our testing and the available documentation, it appears that multi-select is not supported for Web add-ins using the Unified Manifest in New Outlook.

Could you please help clarify the following:

  • Are we correct in understanding that multi-selection is currently not supported for Outlook Web add-ins using the Unified Manifest in New Outlook/Outlook Web?
  • Is there anything we might be missing in the documentation or configuration that would enable this functionality?
  • Is there any recommended workaround to achieve similar behavior?
  • Is there an estimated timeline or roadmap for when multi-select support might become available in this scenario?

Thank you in advance for your guidance.

Kindest regards,

Andjela

Microsoft 365 and Office | Development | Office JavaScript API
Answer accepted by question author
  1. Gabriel-N 14,775 Reputation points Microsoft External Staff Moderator
    2026-03-06T15:11:07.2033333+00:00

    Hello Andjela Mijailovic

    Thank you for your question on Q&A Forum regarding multi-selection support in Outlook Web Add-ins using the Unified Manifest in the New Outlook and Outlook on the Web.

    Based on my research, currently, multi-selection is not supported for Outlook Web Add-ins that use the Unified Manifest in the New Outlook or Outlook on the Web.

    Please refer to the official Microsoft documentation here: Activate your Outlook add-in on multiple messages

    User's imageAs a workaround, Microsoft recommends deploying the Outlook add-in using the traditional XML manifest (also known as the “add-in only manifest”) and setting the <SupportsMultiSelect>true</SupportsMultiSelect> flag. This approach enables multi-selection support across all platforms, even while continuing to use the Unified Manifest for other Office or Teams apps if needed.

    You can find the relevant section in the same article linked above: https://learn.microsoft.com/en-us/office/dev/add-ins/outlook/item-multi-select?tabs=xmlmanifest#configure-the-manifest

    <Action xsi:type="ShowTaskpane">
    <SourceLocation resid="Taskpane.Url"/>
    <SupportsPinning>true</SupportsPinning>
    <SupportsNoItemContext>true</SupportsNoItemContext>
    <!-- Enables your add-in to activate on multiple selected messages. -->
    <SupportsMultiSelect>true</SupportsMultiSelect>
</Action>

    Unfortunately, there is currently no specific timeline announced for when full support for multi-select with the Unified Manifest will be available in the New Outlook or Outlook on the Web. However, the issue has been acknowledged and is currently listed as “in backlog” on GitHub. For your reference, here’s one of the related GitHub threads: Not able to open web add-in after selecting multiple emails in New Outlook #3441

    Hope this information is helpful.

    Note: Please follow the steps in our documentation to enable e-mail notifications if you want to receive the related email notification for this thread.  

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  1. Q&A Assist
    2026-03-06T14:07:36.64+00:00
    AI generated content. This question contains an answer created with AI from Q&A Assist. Learn more

    Item multi-select is supported for Outlook web add-ins in the new Outlook on Windows and Outlook on the web, including in the unified experience, but it must be explicitly enabled and has some client-specific behavior.

    From the available documentation:

    • Outlook web add-ins can be activated on multiple messages at once using the item multi-select feature. This is listed as a supported scenario for project-management and similar workflows in the new Outlook on Windows and Outlook on the web.
    • When item multi-select is enabled, the add-in can run on multiple selected mail items. The task pane behavior depends on the client:
      • On Windows (new and classic) and web, the task pane closes when switching to a new item unless the user pins it. To keep it open, the user must select the pin icon on the task pane.
      • On Mac, the task pane stays open when switching items and must be closed explicitly.
    • Enabling no item context automatically enables item multi-select in Outlook on the web and the new Outlook on Windows. In that case, the add-in is activated from the message action bar after selecting one or more messages.

    The context does not state any limitation that would exclude add-ins using the unified manifest from item multi-select; instead, it describes multi-select as a supported capability for Outlook web add-ins in the new Outlook and web clients.

    For configuration and behavior details, see:

    • Item multi-select behavior and limitations in Outlook clients.
    • Contextless (no item) activation, which also enables multi-select in Outlook on the web and new Outlook on Windows.

    No roadmap or timeline changes beyond these capabilities are provided in the available documentation, and no additional workarounds are documented beyond using item multi-select and contextless activation as described.

    References:

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