Today, One of our user faced problem that when he tried to open certain emails , it gives option to open it in my web browser, rather than within Notes itself. it showed all of the html formatting characters in the notes, rendering it almost unreadable. I applied fresh install of Notes but no use. The client was using Lotus notes 8.5.2
This is how I solved it.
Open Lotus Notes Client
Goto Files / Preferences
In the right window, click on ADDITION OPTIONS, Tick on DISABLE EMBEDDED BROWSER FOR MIME FORMAT”
As showed in the example below , , ,
Now restart Notes Client, and the problem solved 🙂