Outlook Onsend addin is invoked multiple times after clicking send

[AtharvaDevSeclore]

I have developed an add-in for Outlook that is triggered whenever the user clicks the "Send" button. Upon activation, the add-in opens a dialog box that allows the user to interact and input information. The primary function of the add-in is to automatically append a header and footer to the body of the email before it is sent.

However, I’ve encountered an issue where the add-in is sometimes invoked multiple times in quick succession, causing the header and footer to be added repeatedly to the email body. This results in the email body becoming cluttered with redundant content.

For context, I am using Outlook 16.94 with the legacy UI on a Mac system.

I’ve come across a similar issue reported on GitHub (#1367), which appears to be related, though the problem is not entirely consistent. The issue seems to occur more frequently under certain conditions, particularly when multiple applications are running simultaneously. A noteworthy observation is that when the user is sharing their entire screen via Microsoft Teams, this issue becomes almost persistent.

[github-actions]

Here are some similar issues that might help you. Please check if they can solve your problem.

• Currently, the OnSend event fires twice. #3562
• On-Send Event triggers twice on new Outlook for Mac #3753
• Outlook addin is not terminated after timeout #5098

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Possible solution (Extracted from existing issue, might be incorrect; please verify carefully)

Solution 1:

Ensure that all asynchronous API calls are completed before invoking event.completed. Specifically, if the add-in is updating the email body or setting recipients, make sure these operations are finished before calling event.completed.

Reference:

• On-Send Event triggers twice on new Outlook for Mac #3753 (comment)
• On-Send Event triggers twice on new Outlook for Mac #3753 (comment)

Solution 2:

Check if the add-in is deployed twice, such as being both sideloaded and deployed via Office Admin. This can cause the OnSend event to trigger multiple times.

Reference:

• On-Send Event triggers twice on new Outlook for Mac #3753 (comment)

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