Symptoms

1. The email address for the email channel is serviced by office365.com (Exchange Online)
2. When setting up incoming mail retrieval via IMAP, the error is: LOGIN failed.

Solution

You can set up incoming mail collection via SMTP transfer instead of IMAP

Reason

Microsoft has removed the ability to authorize via Basic Auth in Exchange Online:

https://learn.microsoft.com/en-us/answers/questions/1130148/outlook-imap-login-failed-using-python