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The Undo Send function in Outlook Web does not work

confusedshoes 55 Reputation points
2025-08-13T01:51:07.0233333+00:00

In my Outlook web account, I have this 'Undo send' function set to delay sending messages for 10 seconds.

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It works wonderfully for some time until it doesn't.

I can still see the message appears - 'Sending...' and then the 'Undo' link. But I can't click on that "Undo" anymore. It's greyed out.

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Any idea on why I can't click on it anymore? Seems pointless that it's there but can't click on it. Is there something in the settings that I need to change?

Would greatly appreciate if anyone could help me solve this mystery. Thank you!

Outlook | Web | Outlook on the web for business | Email

Answer accepted by question author

  1. Darren-Ng 9,800 Reputation points Microsoft External Staff Moderator
    2025-08-13T03:04:29.1733333+00:00

    Hi @confusedshoes

    Thank you for posting your question in the Microsoft Q&A forum.

    You’re asking why the Undo Send feature in Outlook Web shows the “Undo” link but it’s greyed out and unclickable, even though you’ve set the delay to 10 seconds. Based on the image and description, here are some suggestions:

    • Does this happen only when you pop out the compose window? (That would line up with the known limitation.)
    • Does it happen when sending from a shared mailbox or Send As another address? 
    • Which browser and version are you using?
    • Send a plain text, no‑attachment message to yourself first. If that works, add back attachments, sensitivity labels/encryption, or mentions to see what triggers the behavior.

    Besides that, here are few steps to check and resolve the issue you can try:

    1. Clear browser cache and restart Outlook Web.
    2. Sign out and sign back in to refresh session tokens.
    3. Try another browser or InPrivate mode
    4. Reset Undo Send: Turn it off, save, then turn it on again.

    If none of the above works, contact your IT admin, they might have enforced a transport rule that bypasses the delay.

    And if you're unsure who your Global Admin is, this guide may help How do I find my Microsoft 365 admin? - Microsoft Support   

    I hope information above helpful, if you have any other questions, please feel free to reach out

     

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  1. CJ 0 Reputation points
    2026-02-03T02:53:36.5033333+00:00

    I experienced an issue with the Undo function in Outlook on the web that appears to have been present for some time, likely beginning around September 2025, although I cannot pinpoint the exact start date. My issues seemed to be solely with the "New Mail" button as the open new window option worked fine (for the undo button). I was and still am using Edge for my browser while logged into my work's account.

    I work in a university environment with a significant number of administrative and security controls in place. After reviewing our configurations, I am confident that none of our organizational policies or controls should directly impact this specific Outlook setting.

    After reviewing recommendations from others experiencing similar behavior, testing various configuration changes, and consulting Copilot, I ultimately identified a resolution through direct testing. The issue was resolved by changing the Undo send delay setting from the previously configured 10 seconds to 20 seconds, saving the change, and then refreshing the Outlook on the web session. Once this was done, the Undo button began functioning normally again.

    For clarity and completeness, the issue was highly specific in its behavior:

    • The problem consistently occurred when selecting New Mail and composing an email in the inline compose window.
    • In this scenario, the Undo button was not functional.
    • If the compose window was popped out or opened in a separate window, the Undo functionality worked as expected.
    • When replying to emails using Reply or Reply All, the behavior was inconsistent but generally functional, working approximately nine times out of ten.
    • The failure was isolated almost entirely to newly composed messages, regardless of whether the recipient was internal or external.

    Following the adjustment to the Undo delay setting and a page refresh, the issue has not reoccurred. This suggests the problem may be related to how Outlook on the web initializes or maintains the Undo state within the inline compose experience when using certain delay values.

    I am documenting this here in case it proves useful to others encountering similar behavior in managed or enterprise environments.

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  2. Showalter, Amy 0 Reputation points
    2025-08-26T19:13:45.7666667+00:00

    Same here - worked last week. annnnnd.... now it doesn't.

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