By the end of 2020, Microsoft will no longer support Basic Authentication for many of their services, including POP and IMAP to collect emails or for integrations with their Exchange Online and Exchange Web Services. Google announced very much the same thing in December 2019 but takes it a step further by also disallowing basic authentication for sending email through SMTP.
The alternative for both of these providers is to use OAuth 2.0 as the authentication mechanism. Wim Decorte outlines this process in his Microsoft Graph API for Office 365 Integrations in FileMaker blog series.
Download our demo file for a practical guide to deep integration with the Office 365 APIs and the challenges that you are likely going to encounter with similar APIs.