Do the add-ins work in Office 365?

Yes. We have three categories of add-ins, all of which work in Outlook:

1. Our traditional Outlook add-ins work in the desktop version of Outlook, but will not appear in the web interface of Outlook.That said, there’s nothing wrong with having an Office 365 account as your email server and using the desktop version of Outlook. The add-ins work great under that scenario.
2. Our “modern” style Outlook add-ins work in the desktop version of Outlook, Macs, Outlook on the web, and in some cases, Outlook for Android and iOS.
3. Our cloud services, which aren’t add-in per se, but mimic some add-in’s functionality.  These services reside in our cloud server and access your email to get the job done, 24 x 7 x365.