Office.js add-ins process an email twice after undo-ing mail send and sending again

Hi Raghunandan Kumbhar, 
Thank you for posting your question in the Microsoft Q&A forum. 

Please correct me if I'm wrong, but it sounds like you're experiencing repeated processing of the same email by your Office.js on-send add-in when using the "Undo send" feature in Exchange. Specifically, after undoing a send and resending the email without any changes, the add-in processes it again. 

Based on your description, this behavior is actually expected. 

The on-send feature is designed to intercept every send action, regardless of whether the message has been previously processed. Its purpose is to allow add-ins to validate, modify, or block the message at the moment of sending. It does not track the message history or whether it has already been processed by the add-in. Therefore, when a user cancels the send and then sends again even without changes, the add-in treats it as a new send event and processes it accordingly. 

If you're looking to implement logic that avoids reprocessing identical messages, you might consider adding custom tracking or caching mechanisms within your add-in to detect and handle such cases. 

For more details on how the on-send feature works, you can refer to the official documentation here: On-send feature for Outlook add-ins - Office Add-ins | Microsoft Learn 

I hope the information I've provided is helpful and aligned with what you were looking for. If you have any further questions or need clarification, please don’t hesitate to reach out again. 

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