Is the Microsoft Office 365 Pop3 basic authentication deprecation going to have any impact for sites using Office 365 mailboxes?

Environment:

Office365-hosted Mailboxes
Oracle B2C Service, All versions

Resolution:

Oracle B2C Service is taking a proactive approach to the announcement made by Microsoft to deprecate basic authentication for MS Exchange. While the initial deadline was deferred, support for basic authentication is ending to randomly selected tenants beginning October 1, 2022 and being permanently disabled starting January 1, 2023.  No extensions can be requested as of January 1, 2023.  Details of Microsoft's announcement can be found at:

• https://techcommunity.microsoft.com/t5/exchange-team-blog/basic-authentication-deprecation-in-exchange-online-time-s-up/ba-p/3695312
• Dec-2022: https://learn.microsoft.com/en-us/exchange/clients-and-mobile-in-exchange-online/deprecation-of-basic-authentication-exchange-online
• Sep-2022: https://techcommunity.microsoft.com/t5/exchange-team-blog/basic-authentication-deprecation-in-exchange-online-september/ba-p/3609437

If basic POP is disabled and OAuth is not setup, techmail will be unable to open your mailbox and process emails.  If you have production mailbox(es) impacted by basic POP being disabled, please consider a short-term extension of basic POP if allowable while you setup OAuth for a low-volume or test mailbox.

We introduced OAuth authentication beginning in versions 20C and above. OAuth authentication for Office365 mailboxes is configurable in a new Mailboxes editor available in the Browser UI (BUI).   There is an option to use .NET clients to access the new mailbox editor, but must be enabled as instructed in  Answer ID 11837:  Enabling the mailboxes editor for OAuth in .NET and this step is optional.  If your account does not have access to Browser UI see Answer ID 10927: Needing login access to the Browser UI

1. Create an App Registration on Microsoft's Azure Directory, a description of the items is available in:
   Answer ID 11864:Setting up App Registration for Office365 Mailboxes
2. Create Oracle B2C Service configuration settings as documented at https://documentation.custhelp.com/euf/assets/devdocs/buiadmin/topicrefs/t_configure_oauth_authentication_settings.html 
3. Use the Oracle B2C Service Mailboxes editor to configure the mailbox with OAuth authentication, steps are listed in:
   Answer ID 11864: Setting up App Registration for Office365 Mailboxes
4. Once a mailbox passes OAuth authentication techmail will use an OAuth jwt token to open the mailbox. 
5. If techmail cannot open the mailbox there will be Notifications for the mailbox and techmail:
   1. Check techmail utility stats as instructed in:
      Answer ID 4551: How to check utility status for my site (i.e. Techmail)
   2. Check your notifications for the following message:
      System - Application *your interface name*: *your mailbox POP account name*: Unable to connect to mailbox. Server Error Message:-ERR Logon failure: unknown user name or bad password.