MicrosoftShrade13 Unfortunately, that fix is not available in every 365 build currently deployed and still seems likely to disappear eventually.
If you, and any other recent posters, agree that we need a permanent option to NOT display this 'app' thingy on the left side of the Outlook 365 window, please upvote https://feedbackportal.microsoft.com/feedback/idea/c4da6df0-a9a0-ec11-a81c-000d3a0eaac7 (and forgive the OP's typo in the subject line) . From my earlier reading in this thread, simply lodging your objection in this thread will do nothing to influence the Office people to reconsider their (almost certainly marketing-driven) decision.
On the off chance that typing here actually has any weight with Microsoft, I'd also like to mention the old flies-honey-vinegar addage. My first reaction upon seeing this wasteful, useless UI change was full of spite and coarse words, but I've never found that mode of communication to be helpful when dealing with formal organizations of any kind.
