Emoji reactions not available on Outlook desktop app

Because updating classic Outlook did not restore the button, first determine whether it is missing for every message in the primary Exchange Online mailbox or only for particular messages or mailbox types.

Check the affected message and mailbox

1. In classic Outlook, open a recent message addressed directly to your primary mailbox, preferably from a colleague in the same organization.
2. Look near the top of the message window for the Reactions button.
3. Compare the results:
   • Only shared-mailbox messages are affected: this is expected; reactions are not supported for Microsoft Exchange shared mailboxes.
   • Only some senders or messages are affected: both participants need Exchange Online mailboxes for reactions to work fully. An administrator can also block reactions on selected messages through the x-ms-reactions: disallow header.
   • The button is absent from every message in classic Outlook but present for the same messages on the web and mobile: this points to a classic-client-specific problem rather than general account eligibility.

Reactions require a work or school account, a qualifying Microsoft 365 subscription, and— for full functionality—Exchange Online mailboxes for both parties. They are unavailable in GCC High, DoD, and Gallatin environments and unsupported for shared mailboxes.^1^

There is currently no published Microsoft known issue tying the missing Reactions button to Version 2610 builds 16.0.20527.20150 or 16.0.20527.20196.^2^

Isolate a classic Outlook client conflict

If the button is missing for all eligible messages in the primary mailbox:

1. Close Outlook.
2. Press Windows key + R.
3. Enter:

      outlook.exe /safe
   

4. Open the same message and check for the Reactions button.

Safe mode starts classic Outlook without COM add-ins. If reactions return, disable—not remove—the add-ins under:

File → Options → Add-ins → Manage: COM Add-ins → Go

Then restart Outlook normally and re-enable the add-ins individually until the conflicting one is identified.^3^

If safe mode makes no difference, test with a separate Outlook profile:

1. Create a new classic Outlook profile and add the same work account.
2. Hold Shift while starting Outlook.
3. Select the new profile.
4. Open the same message and check the button.

If reactions work in the new profile, the original profile is damaged; use the new profile rather than reinstalling Office.^3^

Administrator and escalation checks

If the button remains absent in safe mode and a new profile:

• Ask the Microsoft 365 administrator to verify that this is the user’s primary Exchange Online mailbox, not an on-premises or shared mailbox.
• If only certain messages are affected, ask the administrator to inspect their headers and Exchange Online mail-flow rules for x-ms-reactions: disallow. That header blocks reactions at the Exchange Online service layer.^4^
• If every eligible message is affected only in classic Outlook, keep using Outlook on the web as the workaround and open a Microsoft 365 support case. Include both affected build numbers, confirmation that the same message supports reactions on web/mobile, and the results of the safe-mode and new-profile tests.

References

1. Reactions in Microsoft Outlook
2. Fixes or workarounds for recent issues in classic Outlook for Windows ...
3. [Classic Outlook](https://support.microsoft.com/outlook/getstarted/outlook-for-windows-not-responding-hangs-freezes-or-stops-working)
4. Use the x-ms-reactions header to disallow reactions in Outlook