For the year 2020, Microsoft has planned to issue end-of-support to many of its existing functionalities. This is mainly for increasing the security of Office 365 cloud services and for reducing the technical burden of maintaining legacy tools. To name a few, it includes Basic Authentication, Unified Messaging, TLS 1.0 & 1.1, and Office 2016 for Mac.
It's good to keep an eye on the deprecating functionalities and ensure that we are ready for them to avoid late surprises. For example, to prepare for basic authentication deprecation, we need to update our existing Exchange Online scripts, remove app passwords, etc. Fortunately, Microsoft is extending the support for SMTP as a lot of legacy/automated script uses this to send the emails.
My team has compiled all of the deprecating items together and prepared a timeline for 2020. We have also made a cool infographic for easy tracking!