It, along with POP, have been the backbone of the receipt of emails since Day One. Is support for IMAP, iCloud and Exchange coming? It's unclear at this time, but it would be surprising if Microsoft didn't at least support IMAP. In fact, when you install the latest Big Sur build, and then open Outlook for Mac, this is what you see if you have any Exchange accounts set up: It DOES NOT SUPPORT on-premises Exchange accounts or connect to any on-premises mail servers that use Exchange protocols.
It offers ZERO SUPPORT for IMAP or iCloud accounts. The 2 biggest issues with the latest preview of Outlook for Mac are: It also gives some insight into the direction Microsoft is moving, and that direction itself is somewhat disturbing and may have people thinking twice if they want to continue using Microsoft's email clients.
And just as there are some issues with the Big Sur BETA that Apple is working through, the preview of Outlook has some glaring, and extremely alarming, changes that will affect any user of any on-premises email server. The ongoing BETA of the next version of MacOS, Big Sur, comes with the bonus of a preview of the upcoming Microsoft Outlook for Mac.