Using older versions of Outlook for Mac in business environments
I used these references to find an 100% effective solution: https://www.techradar.com/pro/free-email-clients-listed-and-compared https://www.pcmag.com/picks/best-email-clients
i.e. email client software that avoids MS's heavy-handed obnoxiousness.
Thuderbird is powerful but sometimes fiddly.
eM Client is becoming my newest favorite.