I recently encountered the issue, that after setting up Microsoft Exchange Publishing 2016 with NetScaler 11.1 configuring Unified Gateway, entering the "URL for Web Based E-Mail" is not working properly. As soon as I click on the E-Mail Tab in the portal, the side doesn't load properly, staying white. When i click around ,trying to change view etc it somehow loads in a weird transparent display, unable to click anything in it. When i configure the same with a Bookmark (loading in a new tab) everything works fine. With Exchange 2013 everything worked fine with the portal mode / frame-in-frame.
I tried to get rid of the X-Frame-Options Header as I saw in Fiddler that requests with X-Frame-Options Header set to "SAMEORIGIN" caused connection drops. This didn't solve the issue but somehow i have a feeling, that Exchange simply doesn't allow me to display OWA with frame-in-frame. Could anyone configure Exchange 2016 with Web-Mail Portal Mode (Unified Gateway) properly to get it working? Maybe Exchange 2016 via Unified Gateway (with this specific setting) is not supported yet?
Appreciate all your help