Please post your Troubleshooting Information. At the top right of the Thunderbird window, click the menu button ≡, then select Help > More Troubleshooting Information. Press the "Copy text to clipboard button" and paste the information into your reply.

Application Basics

   Name: Thunderbird
   Version: 128.2.3esr
   Build ID: 20240920043836
   Distribution ID:

   Update Channel: esr
   User Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:128.0) Gecko/20100101 Thunderbird/128.2.3
   OS: Windows_NT 10.0 22631
   OS Theme:

   Launcher Process: Enabled
   Multiprocess Windows: 0/0
   Fission Windows: 0/0
             Enabled by default
   Remote Processes: 2
   Enterprise Policies: Inactive
   Google Location Service Key: Missing
   Google Safebrowsing Key: Missing
   Mozilla Location Service Key: Missing
   Safe Mode: false
   Memory Size (RAM): 15.8 GB
   Disk Space Available: 98.5 GB

 Mail and News Accounts
   account2:
     INCOMING: account2, , (none) Local Folders, 0, passwordCleartext

   account4:
     INCOMING: account4, , (pop3) pop-mail.outlook.com:995, SSL, passwordCleartext
     OUTGOING: , smtp-mail.outlook.com:587, alwaysSTARTTLS, passwordCleartext, true

   account5:
     INCOMING: account5, , (pop3) pop-mail.outlook.com:995, SSL, passwordCleartext
     OUTGOING: , smtp-mail.outlook.com:587, alwaysSTARTTLS, passwordCleartext, true

   account6:
     INCOMING: account6, , (pop3) pop-mail.outlook.com:995, SSL, passwordCleartext
     OUTGOING: , smtp-mail.outlook.com:587, alwaysSTARTTLS, passwordCleartext, true

   account7:
     INCOMING: account7, , (pop3) pop-mail.outlook.com:995, SSL, passwordCleartext
     OUTGOING: , smtp-mail.outlook.com:587, alwaysSTARTTLS, passwordCleartext, true

   account8:
     INCOMING: account8, , (imap) imap.gmail.com:993, SSL, OAuth2
     OUTGOING: , smtp.gmail.com:465, SSL, OAuth2, true

 Libraries

     Library
     Status
     Expected minimum version
     Version in use
     Path

       RNP (OpenPGP)
       OK
       0.17.1
       0.17.1.MZLA.128.2.3esr.botan
       C:\Program Files (x86)\Mozilla Thunderbird\rnp.dll

       OTR
       Failed to load. OTR chat encryption will not work.
       -
       -
       -

 Calendar Settings

   Home

     Name
     Value

     Name:
     Type: storage
     Disabled:
     Username:
     URI:
     Refresh Interval:
     Read-only:
     Suppress Alarms:
     Cache Enabled:
     iMIP Identity: id1
     iMIP Disabled:
     iMIP Account:
     Organizer Id:
     Force Email Scheduling:
     Popup Alarms Supported:
     Alarms on Invitation Supported:
     Max Alarms Per Event:
     Attachment Supported:
     Max Categories:
     Privacy State Supported:
     Priority Supported: true
     Event Supported:
     Task Supported:
     Local Time Supported:
     UTC/GMT Supported:
     Auto-Scheduling Supported:

 Crash Reports for the Last 3 Days

 Remote Processes

   Type: Count

     Isolated Web Content: 1
     GPU: 1

 Add-ons

     Name
     Type
     Version
     Enabled
     ID

       Amazon.com
       extension
       1.1
       true
       amazondotcom@search.mozilla.org

       Bing
       extension
       1.0
       true
       bing@search.mozilla.org

       DuckDuckGo
       extension
       1.0
       true
       ddg@search.mozilla.org

       Google
       extension
       1.0
       true
       google@search.mozilla.org

       Wikipedia (en)
       extension
       1.0
       true
       wikipedia@search.mozilla.org

       System theme — auto
       theme
       1.3
       true
       default-theme@mozilla.org

       Dark
       theme
       1.3
       false
       thunderbird-compact-dark@mozilla.org

       Light
       theme
       1.3
       false
       thunderbird-compact-light@mozilla.org

 Security Software

   Type: Name

     Antivirus: Microsoft Defender Antivirus
     Antispyware:
     Firewall: Windows Firewall

 Legacy User Stylesheets

   Active: false
   Stylesheets: No stylesheets found

You do need to fix the server names in your Account Settings for the troubled account(s). Once the server names are correct, you can select OAuth2 for authentication.

Incoming: outlook.office365.com Port: 995 User Name: <your e-mail address> Connection security: SSL/TLS Authentication method: OAuth2

Outgoing: smtp.office365.com Port: 587 User Name: <your e-mail address> Connection security: STARTTLS Authentication method: OAuth2

Thanks Christ1 for your time and effort. I do not know why only one account was affected but your solution did the job. You were clear and concise, Much appreciated, keep up the good work!