Sage has received updated guidance from Microsoft specific to our use of SMTP Auth for email integration between Sage 100 and 300 and Exchange Online. At this time, Microsoft will not block active accounts using SMTP Auth. This means that Sage 100 and 300 customers utilizing in-product email services to send quotes, invoices, etc. do not face a shutdown of this functionality beginning on October 1, 2022.
While this guidance also applies to other applications, like Sage Intelligence, that utilize SMTP Auth for email communication, customers need to be aware that many online services will be impacted, so while Sage 100 and 300 are safe in the near term, other client applications using POP, IMAP, etc. can be impacted starting 10/1.
The latest information from Microsoft, including which services are impacted and what to do in the event that a customer is inadvertently blocked, can be found here: https://techcommunity.microsoft.com/t5/exchange-team-blog/basic-authentication-deprecation-in-exchange-online-september/ba-p/3609437