Deprecation of Basic Authentication in Exchange Online
assess potential impact as the Oracle postfix uses OAuth to authenticate the transactional relay accounts.
https://support.microsoft.com/en-au/help/4521831/exchange-online-deprecating-basic-auth
What does it effect?
In short, no more Basic Authentication for the following protocols to access Exchange Online.
EWS (Exchange Web Services)
EAS (Exchange ActiveSync)
IMAP4
POP3
RPS (Remote PowerShell)
Most client apps use Basic Authentication to connect to servers, services, and endpoints as it is simple to set up. Basic Authentication in Exchange Online sends username and password with every client access request.
The alternative to basic authentication is modern authentication for which all of the office applications now support and likely we are already using.