simplest solution (enabling also the standard calendar functionality of ETAR) is installing gmail app (sorry) and install your office365 outlook business account in gmail.
this will automatically enable calendar info to etar.
Reason for me not to use the outlook app, is the very bad calendar view.
I do not use a google account with the gmail app.
If you don’t need calendar and task / notes functionality of your outlook account, you can use the standard email app for connecting to the imap settings as mentioned in the chat above. You will then not need the Gmail app.
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