I need step-by-step instructions to get CLAWS mail 4.1.0 working with outlook.office365.com
for IMAP

I have tried
https://office365.mcmaster.ca/reconf...uthentication/

and

https://www.claws-mail.org/faq/index.php/Oauth2
( do I really need to register CLAWS MAIL on the server? )

but no joy... part of the problem is that I can't tell what to leave <blank> and how to interpret the claws log (other than OAUTH2 is not set up correctly )

OAuth2 error. Check and correct your OAuth2 account preferences.
IMAP> Logging xxxxxxxx to outlook.office365.com using XOAUTH2
IMAP< AUTHENTICATE failed.
** IMAP error on outlook.office365.com: LOGIN error
IMAP< Error logging in to outlook.office365.com
*** Couldn't login to IMAP server outlook.office365.com.
IMAP> 4 LOGOUT
IMAP< * BYE Microsoft Exchange Server IMAP4 server signing off.
IMAP< 4 OK LOGOUT completed.

Claws Mail user here.

I would suggest searching the claws Mail mailing list archives. There has been a lot of discussion in the list. Better yet join and post the question there. https://www.claws-mail.org/MLs.php

I have three Outlook accounts so far none have required me to use OAUTH2 (I use POP3 for these account). Gmail on the other hand stopped working. For Gmail is does require your to register Claws Mail on the server. I cold only get it to work for 7 days and had to resent my key. I finally gave up and opted for 2FA and use an Application Password for Claws Mail.

Recently I had a temporary assignment at a university where the staff mail used outlook.office365. In order to get the mail to my Thunderbird I had to set up davmail, see http://davmail.sourceforge.net/index.html

Don't know if this will work on claws as well but might be worth a try.