How to access Shared Inboxes with OAuth via IMAP (Basic Authentication Deprecation)

[Bergkuh]

Since Microsoft is deprecating basic auth in the future I cannot use IMAP to access shared inboxes the way I used to:

Email address: sharedmailbox[AT]domain.com

Incoming Mail Server (IMAP)

Username: mymailbox[AT]domain.com/sharedmailbox

Hostname: outlook.office365.com

Outgoing Mail Server (SMTP)

Username: mymailbox[AT]domain.com

Hostname: outlook.office365.com

In order for the above to work I had to disable security defaults. By 01. October this will stop working.

I use the native Apple mail app for managing mails. Now for the life of me I cannot figure out how I could possibly access shared inboxes via OAuth. When I choose to add an "Microsoft Exchange" account (which is the only way I found to use OAuth) I put in sharedmailbox[AT]domain.com as the mail address (which is the shared inbox I want to manage) and as username I choose my account mymailbox[AT]domain.com. When I do that the mail address is simply ignored and I end up adding my personal mailbox instead of the shared mailbox. Trying to login as mymailbox[AT]domain.com/sharedmailbox doesn't work either.

Has anyone an idea how to get this working? I'm really used to working with my separate mailboxes and I really can't afford to put licenses on them.

[#2]

@Bergkuh 
I don't know if you have found the solution, but if you don't this is what you need to do : change the user name and change the authentication method.
before it was:
user name: email address removed for privacy reasons\mySharedBoxName 
Authentication method: "normal password" (I think it is also called "Basic Authentication" on some messaging system")

now it is:
user name: mySharedBoxName @mydomain.com 
Authentication method: "OAuth2"

Then you need to restart you messaging app, first time it will ask you to log in office365.Be carefull OAut2 redirection will propose you to sign in with email address removed for privacy reasons, you need to  use your own email (in my example email address removed for privacy reasons ) with your own password.

[#3]

@Laurent_Salvinien 

We are having the same issue with the email integration with Oracle Webcenter Capture.  we could use email address removed for privacy reasons\sharedmailbox with IMAP basic auth that worked fine but now with OAUTH we are unable to access.  Error is:

[APP: capture] [partition-name: DOMAIN] [tenant-name: GLOBAL] error_description: AADSTS900023: Specified tenant identifier 'domain.com\\sharedmailbox' is neither a valid DNS name, nor a valid external domain.

We also tried with just one \ and the same message comes in.

We don't have direct access to the shared mailbox.  Is there a way to pass the shared mailbox with oauth.  The email address removed for privacy reasons doesn't really have access to mail and isn't a destination for incoming mail.

Thank you

Tom