We are publishing outlook add-in and its gets rejected saying it's not visible in outlook 2016 MSI. Does it has something to do with the mailbox version as we are using 1.6 ??
Outlook 2016 one-time purchase supports only 1.1, 1.2, 1.3, 1.4.
Read more about that in the Outlook JavaScript API requirement sets article.
If you are still interested in installing Office 2016, see Download and install or reinstall Office 2016 or Office 2013.