Office 365 authentication prompt when opening documents

In our environment we are using Office 365, we configured ADFS / ADFS Proxies / and Dirsync to manage SSO.

We have constructed smart links to ensure users are automatically signed into SharePoint when using their work laptop and Internet Explorer – if they are using a difference device / browser then they are directed to the corporate login page.

We experienced an issue where customers would be requested to sign into Word / Excel / PowerPoint when opening files directly from SharePoint.

This was resolved my modifying the smart links to contain 



Example smart link:

more info on smart links