Microsoft has announced that they will begin deprecating Basic Authentication (Username/Password) methods for sending emails via SMTP through their Exchange services, which will affect our Office 365 customers.
https://learn.microsoft.com/en-us/exchange/clients-and-mobile-in-exchange-online/deprecation-of-basic-authentication-exchange-online
We need to look into implementing a way to send emails utilizing OAuth so our customers have the ability to configure SMTP to comply with Microsofts recommendations.