Please see https://wiki.mozilla.org/Thunderbird:Testing:Memory_Usage_Problems

Thanks for trying - but not helpful: mostly very generic, or does not apply to my configuration, or too painful to consider e.g creating a new profile. Appears problem started with the Thunderbird update I installed 11/20/25, or possibly the latest Win 11 security update 11/12/2025 (or, unlikely, Win 11 feature update 11/19/2025). I am only running Windows Defender (no other firewalls or antivirus/malware programs). The last Windows defender security alert was 9/15/2021. There have been no Windows crash reports since 3/13/2025. Safe mode doesn't help, nor does working off-line. I keep my spam and trash folders clean more than daily. No themes, calendars or add-ons are used. Thunderbird behaves totally normally for all receiving and sending, storing, retrieving and file folder functions - the problem is only when typing or editing a new message and can occur after two or as many as 10 lines of text (no special fonts or characters used). When it crashes, there is no unusual or interesting activity seen in task manager (so I could have grabbed a screen shot).

Attached is the Thunderbird-generated troubleshooting information (excluding the final "graphics information - file too big to attach). Hope you can help!:

 Application Basics

   Name: Thunderbird
   Version: 140.5.0esr
   Build ID: 20251108022659
   Distribution ID:

   Update Channel: esr
   User Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:140.0) Gecko/20100101 Thunderbird/140.5.0
   OS: Windows_NT 10.0 26200
   OS Theme:

   Launcher Process: Enabled
   Multiprocess Windows: 0/0
   Fission Windows: 0/0
             Enabled by default
   Remote Processes: 1
   Enterprise Policies: Inactive
   Google Location Service Key: Missing
   Google Safebrowsing Key: Missing
   Mozilla Location Service Key: Missing
   Safe Mode: false
   Memory Size (RAM): 31.8 GB
   Disk Space Available: 653 GB

 Mail and News Accounts
   account1:
     INCOMING: account1, , (pop3) pop.mail.yahoo.com:995, SSL, passwordCleartext
     OUTGOING: , smtp.mail.yahoo.com:465, SSL, passwordCleartext, true
     OUTGOING: , smtp.mail.yahoo.com:465, SSL, passwordCleartext, false

   account2:
     INCOMING: account2, , (none) Local Folders, 0, passwordCleartext

   account3:
     INCOMING: account3, , (pop3) pop.mail.yahoo.com:995, SSL, passwordCleartext
     OUTGOING: , smtp.mail.yahoo.com:465, SSL, passwordCleartext, true

   account5:
     INCOMING: account5, , (pop3) pop.gmail.com:995, 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.140.5.0esr.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: id2
     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

   GPU: 1

 Add-ons

     Name
     Type
     Version
     Enabled
     Location
     ID

       Light
       theme
       1.3
       true
       app-builtin
       thunderbird-compact-light@mozilla.org

       Amazon.com
       extension
       1.1
       false
       app-builtin
       amazondotcom@search.mozilla.org

       Bing
       extension
       1.0
       false
       app-builtin
       bing@search.mozilla.org

       DuckDuckGo
       extension
       1.0
       false
       app-builtin
       ddg@search.mozilla.org

       Google
       extension
       1.0
       false
       app-builtin
       google@search.mozilla.org

       Wikipedia (en)
       extension
       1.0
       false
       app-builtin
       wikipedia@search.mozilla.org

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

       System theme — auto
       theme
       1.4.1
       false
       app-builtin
       default-theme@mozilla.org

 Security Software

   Type: Name

     Antivirus: Microsoft Defender Antivirus
     Antispyware:
     Firewall: Windows Firewall

 Legacy User Stylesheets

   Active: false
   Stylesheets: No stylesheets found

 Graphics

Try this:

- go to TB menu > Settings > General

- scroll all the way down and click the 'Config editor' button on the right

- click 'Accept the risk and continue' if that appears

- search for accessibility.force_disabled > change the value to 1 > click the check mark

- restart TB

That seems to have solved it - will report later if problem recurs over time. I'd have never found this solution without your help - Thank You!!

That seems to have solved it - will report later if problem recurs over time. I'd have never found this solution without your help - Thank You!!

It's actually a bug. It may help the developers if you:

- change accessibility.force_disabled back to 0

- click TB menu > Help > Troubleshooting information

- press Ctrl-F and search for accessibility

- press Enter 3-4 times until you get to the Accessibility section

- copy what's in the four boxes and paste that here

- close that tab and revert accessibility.force_disabled back to 1

I hope this is what you requested - and that it helps resolve the problem for others so effected:

I hope this is what you requested - and that it helps resolve the problem for others so effected:

That's it - thanks.