Outlook email is delayed while a web add-in is working on the send request

Last Updated: June 13, 2024

ISSUE

After you click to Send an email, the email form does not close, and you may get a message indicating that an add-in is working on the send request. The delay after you select Send can be from 30 minutes up to 4 hours. When a user is in this state and they attempt to send an email, the form will stay up indefinitely. This happens because the OnSend add-ins will timeout after 5 minutes. Selecting the Send button again will not help until the issue is resolved. After 30 minutes to 4 hours and depending on the cache expiration for MetaOS, the web add-ins on the user’s machine will be refreshed. At this point selecting the Send button again will re-run the OnSend add-ins again and they will succeed, and the email will be sent. New emails will also be sent successfully.

This issue can impact users on any Office channel that supports MetaOS and that use OnSend action Web add-ins. The only channel that does not have MetaOS yet is Semi-Annual Enterprise Channel.

This issue has been in the product for a few years but has only started to be observed in Version 2404 Build 17531.20000 and higher.

STATUS: FIXED

This issue is fixed in the following Microsoft 365 Channels. We will update the fixed build for Monthly Enterprise Channel as soon as it is available.

This issue is fixed in the following builds:

Beta Channel: 17802.15030, Update history for Office Beta Channel
Current Channel (Preview): 17726.20074, Release Notes Current Channel (Preview)
Current Channel: 17628.20144, Update history for Microsoft 365 Apps (listed by date)
Monthly Enterprise Channel: Currently expected to be fixed in the July 9th public update.

To work around the issue, identify the add-in that has an On-Send action and uninstall it until the fix is available. Alternately you could wait for about 30 minutes to 4 hours for the add-ins to be refreshed on the Outlook Desktop client. Afterwards, new emails will be sent with no problem. In the meantime, use Outlook web app or new Outlook and then switch back to Outlook Desktop after that time has passed.

Another option to help verify the issue would be to revert Outlook to a build before 17531.20000. For example, try reverting to Version 2403. This example below is for Monthly Enterprise Channel. For more information, go to Update history for Microsoft 365 Apps (listed by date).

To work around the issue for Current Channel, use the steps below to revert to the prior working build:

From the Windows search box type Command Prompt, right click Command Prompt and select Run as administrator.
Paste the commands below into the Command Prompt window and press Enter after each:
- cd %programfiles%\Common Files\Microsoft Shared\ClickToRun
- officec2rclient.exe /update user updatetoversion=16.0.17425.20236