On 10/10/2022, Microsoft will be turning off basic authentication for the following protocols: MAPI, RPC, Offline Address Book, Exchange Web Services, POP, IMAP, Exchange ActiveSync and Remote PowerShell. Any client (user app, script, integration, etc.) using basic auth for an affected protocol will be unable to connect to Exchange Online. The client will receive an HTTP 401 error: bad username or password. Any app using modern auth for these protocols will be unaffected. It is recommended you switch to one of the provided methods of connectivity listed at the end of this article.
Basic Authentication is an outdated industry standard. More can be read on Microsoft blog post titled ‘Improving Security – Together’.