We have received a few reports that authenticating with Microsoft’s free email services via username and password has become more challenging recently due to their increased security. We have put together a quick knowledge base doc to make things easier. You can check it out here:
Important to note that this is a general IMAP authentication challenge, not something specific to FEC. On a related note, a separate provider for Microsoft’s email services using Microsoft Graph REST API is on our radar for short to medium term development. Give it an upvote on our Idea Board if interested!