Step by step guide for use with headless davmail?

With manual mode you just have to paste the code from o365psauth.ps1 script into DavMail dialog.

If you want to do this in full headless mode I would suggest using token mode:

.\o365psauth.ps1 -Token
grab refresh_token value from json output
on server with headless DavMail instance, add a line to configuration file: davmail.oauth.username@company.com.refreshToken=_refreshtoken

... or just copy and paste the value obtained in manual mode to target server davmail.properties configuration file.

mguessan / o365psauth