Microsoft wants to remove basic authentication from Exchange Online connection protocols. But pressures have forced Microsoft into a new strategy and away from the mid-2021 date for deprecation of basic authentication for five protocols. Instead, Microsoft will disable basic authentication for protocols where it’s not used, include four addition protocols in its target set, and pause action for tenants where basic authentication is in active use. When they restart, Microsoft will give tenants 12 months’ notice that basic authentication will be blocked for a protocol. You can argue that Microsoft should have pressed ahead with their original plan, but would widespread disruption of service be worth the benefit gained from blocking vulnerable protocols? Balancing risk versus reward is often not easy.
Microsoft has announced that basic authentication for multiple email connection protocols won’t be supported after October 13, 2020. You won’t be able to connect with EWS, EAS, IMAP4, POP3, or Remote PowerShell unless you use modern authentication. There’s just over a year to prepare, but there’s some work to be done.