Using Classic Outlook on Windows for personal email, calendar, and contact management
Hello Rich,
Thank you so much for you updates and patience.
I tried to use both migrated user mailbox and shared mailbox to do the tests on my lab, and as far as I know the tracking button not appears in the sent items folder of the shared mailbox after any of the recipient voted/responded by default, even I tried to manually add the tracking button for the sent items folder for the shared mailbox, it is greyed out, when I double click the sent email to check it.
And based on my tests, I found the same scenario as you, the user's sent items would see the tracking button after the recipients responded, and also the responded emails received in the inbox folder of the shared mailbox would also could help us to track the response if you have the full access permission to open the shared mailbox in your Outlook ( click the sender responded: xx ). For your reference
Please feel free to let me know if you have any other concern, and also thanks for your understanding and patience.
Best Regards,
Oliver