The Undo Send function in Outlook Web does not work

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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