Adding recipient in OnMessageSend times out the add-in

[avisheknand]

We would like to add a recipient to the email on the OnMessageSend event. When we do so, the event.completed executes but still shows the Addin is processing and times out. Can we add recipients in OnMessageSend event?

This issue happens on OWA , New Outlook for Windows. It works fine on the Classic Outlook for Windows

Your Environment

• Platform [PC desktop, Mac, iOS, Office on the web]: OWA
• Host [Excel, Word, PowerPoint, etc.]: Outlook
• Office version number: ______
• Operating System: Win 11
• Browser (if using Office on the web): Edge

Below is the code i have:

Below is the behavior when sending email

[pepso]

@avisheknand It's possible you hit this bug (the right hand side / yellow warning): #4669 (comment)

Try to remove the recipient launch event and see if that fixes the issue to confirm the root cause.

While your onMessageSendHandler is being executed, the add recipient triggered another launch event (OnMessageRecipientsChangedHandler), which invalidated the event handler context your onMessageSendHandler is trying to call to complete the event before it got that far.

[avisheknand]

@pepso,I guessed that as well. It seems the OnMessageRecipientsChangedHandler is causing a conflict. The only way to make it work is to completely remove the event from the manifest file:
<LaunchEvent Type="OnMessageRecipientsChanged" FunctionName="OnMessageRecipientsChangedHandler" />.
When I removed it from the manifest, I was able to add the recipient via the onMessageSend event.
Note: Commenting out the OnMessageRecipientsChangedHandler in the JS will not work; it needs to be completely removed from the manifest.

It’s strange that it works fine in Classic Outlook without removing the handler, but Classic Outlook uses a different environment to run this event compared to New Outlook and OWA.