I've submitted my outlook add-in 6 times now and every time the certification failed for a different reason. The last rejection reason I got was that my add-in didn't work on Office 2013 and Office 2016 (which they also refer to as O365 Perpetual).
I develop on a Mac and I have no idea how to go about debugging why my add-in is not working on those older Offices. Can't I just drop support for older Office suites? How could I test these environments?
I'm pretty close to quitting and just not publishing my outlook addin. I have never experienced a worse app review process.