Exchange Transport News from Microsoft Ignite 2019

Carlos_Capellan The work being done above is aimed at turning off SMTP Auth capabilities for mailboxes that do not need to use it. You can continue to use it for any clients or devices that need to use it. There is a separate effort to disable all basic auth across Office 365. That would have lead to the phasing out of SMTP Auth but an exception was granted because of the widespread usage and lack of a modern auth alternative for SMTP Auth.

There is no need to stop using it anytime soon. Eventually you may have to make the decision between an on-premises relay or a 3rd party service but that is still a few years away. If you were asking from a security point of view, I would suggest hosting your own Exchange Server on-premises that accepts SMTP Auth submissions only from your network and then block all submissions to Office 365.

Hope this clarifies the situation.