As far as I’m concerned, one of the single best reasons to use Microsoft Outlook with Exchange mail hosting is the concept of categories.
It doesn’t seem like rocket science, so I don’t know why other mail systems don’t have anything equivalent. Outlook just allows any contact (or anything else) to be tagged with an arbitrary number of categories of your making, like “Customer – West Coast” or “Holiday List 2018” or “Friends & Family” or what have you.
Then, you just click in the left sidebar which category, or categories, you want to see, and your contact list is automatically filtered. Nifty, amirite?
Well, Microsoft doesn’t seem to have thought so, because, starting in Outlook for Mac 16.20 (December 2018), they removed the category filters. For the love of all things right and true, why? You can still categorize contacts, but, as far as I can tell, you can’t quickly generate a list of the contacts in the categories you want, other than by doing an Advanced Find and searching for them.
If having categories in the left sidebar is part of your workflow, there’s a workaround, at least for a little while. Go to Microsoft’s “Office 2016 update history”, [https://docs.microsoft.com/en-us/officeupdates/release-notes-office-2016-mac] and download the latest version of Outlook (at the time of this writing, 16.16.8). The 16.16.x line of releases continues to receive security updates, but not feature changes. You can have Outlook 16.16.x without needing to install older versions of the other Office apps by downloading just the Outlook installer, rather than the whole suite.
If you have Microsoft AutoUpdate set to update automatically, you’ll want to set it to the middle setting, so it notifies you about updates, rather than just installing them. You can update the other Office apps when it prompts you; just always uncheck Outlook.
If you want to make sure you always have the latest security updates for Outlook, you can manually return to the Outlook 2016 history page and download the latest version of 16.16.x.