Have you tried windows safe mode with networking? I suggest you do.

Can I ask why are suggesting that might help please? Are you suggesting that to run Thunderbird I will always need to run in Safe mode?

I have already done the obvious and checked that Email and calender services are enabled in the Win Defender firewall.

... I should also add that this is not a new problem - it has existed since i first installed TB when this machine was new and had almost nothing else installed. I have raised the matter only now simply becuase it has finally driven crazy ...

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

Wayne Mery; thank you for that link. However, it seems to refer to Thunderbird performance issues. I specifically stated that my problem is that Thunderbird hangs my WHOLE MACHINE. That is a highly specific problem and I cannot see any reference to that in the 4850 words within that link. In fact, when my machine is not hung by it, Thunderbird performs very well indeed.

Could someone please address my specific question???

Applications which induce OS hangs (almost) always have a fundamental underlying problem in the OS.

So the advice Matt provided earlier is spot on - first test is you running Windows in safe mode with networking enabled. (That advice is also in the checklist)

Wayne Mery, many thanks for your further response.

I confess to feeling just the slightest bit frustrated by this. Bearing in mind that this is an intermittent issue, it is 'almost impossible' to test in Safe Mode because the environment is so limiting - for example, I cannot (say) run a music streaming app, or a graphic-dependent app to see if they 'hang' when I send external emails to TB, nor can I get on with any useful work whilst TB runs in the background.

I fully agree that TB has a " fundamental underlying problem in the OS ". However, Safe Mode is not the Operating System I normally use, and not a single one of the other (several dozen) Apps I run has any such problem in normal mode.

I would like to move to the next step please, so let me say "I have been unable to reproduce the fault through the very limited testing I have been able to do in Safe Mode". ... which does not mean that the problem does not exist in Safe Mode - merely that I have no means of surfacing it without wasting half a day typing into TB or some such.

I would add that for 99% of the time, I cannot reproduce it in normal mode either. But it is the 1% which is the nuisance.

Wayne Mery, many thanks for your further response. I confess to feeling just the slightest bit frustrated by this. Bearing in mind that this is an intermittent issue, it is 'almost impossible' to test in Safe Mode because the environment is so limiting - for example, I cannot (say) run a music streaming app, or a graphic-dependent app to see if they 'hang' when I send external emails to TB, nor can I get on with any useful work whilst TB runs in the background.

I don't think Windows safe mode should limit your ability to run graphics.

Any, there is no other next step, if for no other reason than because the OS is hung, how could you possibly get a stacktrace of Thunderbird.

If Windows doesn't hang with OS started in Safe mode, and this can be repeated at a length of time which longer than the typical time that it would hang when not running in Safe Mode, then I think you have your answer - that the cause is not Thunderbird. There is no other way to slice it.

Also:

• run every full computer diagnostic that is possible
• ensure every driver is up to date by checking in Windows, AND the tool(s) supplied by the manufacture of your hardware
• Defender is your only antivirus?

This is very unhelpful. Needless to say, I have already run Windows healthchecks and checked the drivers BEFORE I posted here If, as you seem to suggest, the problem lay with some element of my system, surely at least some other applications would also cause similar issues? To suggest that I completely check-out every element of my system in the hope of stumbling across an issue because just one application hangs is preposterous: surely I only need check the system elements upon which TB depends - so please supply a checklist and I will gladly test to that,

Just to say: so you cannot understand why safe mode limits graphics use? Even though it will only run at VGA resolution? And even though most programmes use drivers which are disabled in Safe Mode? I simply cannot understand why you say such a thing.

You provided no information about what diagnostics you tried and no hard details about your hardware (graphics, etc), so we run with what we know about the state and quality of your system which is incomplete.

> Are you suggesting that to run Thunderbird I will always need to run in Safe mode?

Safe mode is a diagnostic tool, and a standard recommendation. It is never a suggestion to forever run in safe mode.

I've reread you initial posting and identified what might be three key descriptions of the behavior. And number four is this statement, "it has existed since i first installed TB when this machine was new and had almost nothing else installed". So the issue is two years old.

None of these are what we would call a computer hang, nor a crash.

Before we continue, I come back to the question, "is Defender is your only antivirus?".

Sorry - I did not answer your question - yes I only use Defender. I re-iterate that no other application which I use shows any unnexpected behaviour whatsoever.

My definition of a "hang" is that my machine suspeds everything (does not respond to mouse, MIDI or any other input, and produces no output (sounds, screen re-draws etc) for a short period.

Wayne, thank you for your ongoing interest.

Just to clarify - I have never said that TB "crashes" my machine - it certainly does not. What it does is to temporarily suspend all activity on my machine for up to a second, sometimes for several short (say less than 1/2 second) periods in quick succession, after which everything reutrns to normal and will remain so - sometimes for hours without an repeat. However, it typically happens two or three times in a four hour working session, but not "always" and sometimes more frequently.. These episodes are not regular, are not predictable and I cannot pin down exactly what TB is trying to do when the problem occurs. Although I did think it was when incoming e mails were being procesed, that is not always the case by any means.

I have run Windows Reliability Monitor and perfmon/report. I have also been through the drivers via Device Manager. That is the limit of my technical knowledge - if you need other things looking at, you need to tell me what and how. Simply saying "go away and check your system" is not helpful. So thank you for your responses so far, but am hoping for something more definite to try.

1. Give us your hardware specs - Manufacturer, model #, CPU, disk, graphics model/type and driver version+date.

2. Post in this question the output of Help > Troubleshooting Information (there is a "copy text" button")

3. In Thunderbird Settings > General, what is the current state of these four items (b+c+d are near the bottom): a) "Allow Windows to search messages" (near the top), b) "Compact all folders", c) "Enable Global Search", d) "Use hardware acceleration"?

Also, uncheck (disable) all of them. Restart.

4. In Windows, start task manager, click the details tab, order the processes by memory used such that Thunderbird stays visible. a) In a "normal" functioning" state, how much memory and CPU are Thunderbird using? b) When there are problems, how much memory and CPU are Thunderbird using? (forget perfmon and all those other fancy tools)

Thanks for your continued support.

Machine details

Win 11 Pro Version 10.0.26200 Build 26200 Processor Intel(R) Core(TM) i5-10600K CPU @ 4.10GHz, 4104 Mhz, 6 Core(s), 12 Logical Processor(s)

BaseBoard Manufacturer ASUSTeK COMPUTER INC. BaseBoard Product TUF GAMING B560-PLUS WIFI

Installed Physical Memory (RAM) 64.0 GB

Video Adapter:- Adapter Description NVIDIA T400 Adapter RAM (2,147,483,648) bytes Driver Version 30.0.14.9709

Drives:- Drive C: Description Local Fixed Disk Compressed No File System NTFS Size 460.50 GB (494,452,862,976 bytes) Free Space 198.58 GB (213,226,401,792 bytes) Volume Name Windows Volume Serial Number BE51ABBD

Drive D: Description Local Fixed Disk Compressed No File System NTFS Size 931.50 GB (1,000,186,310,656 bytes) Free Space 681.95 GB (732,233,691,136 bytes) Volume Name Storage Volume Serial Number AA200C92

Drive E: Description Local Fixed Disk Compressed No File System NTFS Size 925.65 GB (993,910,583,296 bytes) Free Space 384.13 GB (412,455,669,760 bytes) Volume Name Windows Volume Serial Number 4CC021A3

Thunderbird settings and info:-

Current state 

a) "Allow Windows to search messages"  unticked
b) "Compact all folders",   when it will save > 500MB, Ask every time.

c) "Enable Global Search", ticked d) "Use hardware acceleration"? ticked

I have now disabled the above and restarted.

Troubleshooting info:-

 Application Basics

   Name: Thunderbird
   Version: 140.9.1esr
   Build ID: 20260404050724
   Distribution ID:

   Update Channel: esr
   User Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:140.0) Gecko/20100101 Thunderbird/140.9.1
   OS: Windows_NT 10.0 26200
   OS Theme:

   Launcher Process: Enabled
   Multiprocess Windows: 0/0
   Fission Windows: 0/0
             Enabled by default
   Remote Processes: 3
   Enterprise Policies: Inactive
   Google Location Service Key: Missing
   Google Safebrowsing Key: Missing
   Mozilla Location Service Key: Missing
   Safe Mode: false
   Memory Size (RAM): 63.9 GB
   Disk Space Available: 199 GB

 Mail and News Accounts
   account2:
      [INFO DELETED]

   account6:
    [INFO DELETED]

   account8:
  [INFO DELETED]

   account9:
    [INFO DELETED]

   account10:
      [INFO DELETED]

   account11:
   [INFO DELETED]

   account12:
      [INFO DELETED]

[INFO DELETED]

 Libraries

     Library
     Status
     Expected minimum version
     Version in use
     Path

       RNP (OpenPGP)
       OK
       0.17.1
       0.17.1.MZLA.140.9.1esr.botan
       C:\Program Files\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: id5
     iMIP Disabled:
     iMIP Account:
     Organiser 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
     RDD: 1

 Add-ons

     Name
     Type
     Version
     Enabled
     Location
     ID

       British English Dictionary (Marco Pinto)
       dictionary
       4.0.6
       true
       app-profile
       marcoagpinto@mail.telepac.pt

       Amazon.co.uk
       extension
       1.1
       true
       app-builtin
       amazon@search.mozilla.org

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

       Chambers (UK)
       extension
       1.0
       true
       app-builtin
       chambers-en-GB@search.mozilla.org

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

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

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

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

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

       Light
       theme
       1.3
       false
       app-builtin
       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

 Graphics

     Features
     Compositing: WebRender
     Font Visibility Debug Info: Windows Platform
     Asynchronous Pan/Zoom: wheel input enabled; touch input enabled; scrollbar drag enabled; keyboard enabled; autoscroll enabled; smooth pinch-zoom enabled
     WebGL 1 Driver WSI Info: outOfProcess: false

inProcess: true EGL_VENDOR: Google Inc. (NVIDIA) EGL_VERSION: 1.5 (ANGLE 2.1.19739 git hash: 419cd2c3213b) EGL_EXTENSIONS: EGL_EXT_create_context_robustness EGL_ANGLE_d3d_share_handle_client_buffer EGL_ANGLE_d3d_texture_client_buffer EGL_ANGLE_surface_d3d_texture_2d_share_handle EGL_ANGLE_query_surface_pointer EGL_ANGLE_window_fixed_size EGL_ANGLE_keyed_mutex EGL_ANGLE_surface_orientation EGL_ANGLE_direct_composition EGL_ANGLE_windows_ui_composition EGL_NV_post_sub_buffer EGL_KHR_create_context EGL_KHR_image EGL_KHR_image_base EGL_KHR_gl_texture_2D_image EGL_KHR_gl_texture_cubemap_image EGL_KHR_gl_renderbuffer_image EGL_KHR_get_all_proc_addresses EGL_KHR_stream EGL_KHR_stream_consumer_gltexture EGL_NV_stream_consumer_gltexture_yuv EGL_ANGLE_stream_producer_d3d_texture EGL_ANGLE_create_context_webgl_compatibility EGL_CHROMIUM_create_context_bind_generates_resource EGL_CHROMIUM_sync_control EGL_EXT_pixel_format_float EGL_KHR_surfaceless_context EGL_ANGLE_display_texture_share_group EGL_ANGLE_display_semaphore_share_group EGL_ANGLE_create_context_client_arrays EGL_ANGLE_program_cache_control EGL_ANGLE_robust_resource_initialization EGL_ANGLE_create_context_extensions_enabled EGL_ANDROID_blob_cache EGL_ANDROID_recordable EGL_ANGLE_image_d3d11_texture EGL_ANGLE_create_context_backwards_compatible EGL_KHR_no_config_context EGL_KHR_create_context_no_error EGL_KHR_reusable_sync EGL_EXTENSIONS(nullptr): EGL_EXT_client_extensions EGL_EXT_device_query EGL_EXT_platform_base EGL_EXT_platform_device EGL_ANGLE_platform_angle EGL_ANGLE_platform_angle_d3d EGL_ANGLE_platform_angle_d3d11on12 EGL_ANGLE_platform_angle_device_id EGL_ANGLE_device_creation EGL_ANGLE_device_creation_d3d11 EGL_ANGLE_experimental_present_path EGL_KHR_client_get_all_proc_addresses EGL_KHR_debug EGL_ANGLE_feature_control

     WebGL 1 Driver Renderer: Google Inc. (NVIDIA) -- ANGLE (NVIDIA, NVIDIA T400 Direct3D11 vs_5_0 ps_5_0, D3D11-30.0.14.9709)
     WebGL 1 Driver Version: OpenGL ES 3.0.0 (ANGLE 2.1.19739 git hash: 419cd2c3213b)
     WebGL 1 Driver Extensions: GL_AMD_performance_monitor GL_ANGLE_base_vertex_base_instance GL_ANGLE_base_vertex_base_instance_shader_builtin GL_ANGLE_client_arrays GL_ANGLE_copy_texture_3d GL_ANGLE_depth_texture GL_ANGLE_framebuffer_blit GL_ANGLE_framebuffer_multisample GL_ANGLE_get_serialized_context_string GL_ANGLE_get_tex_level_parameter GL_ANGLE_instanced_arrays GL_ANGLE_lossy_etc_decode GL_ANGLE_memory_size GL_ANGLE_multi_draw GL_ANGLE_multiview_multisample GL_ANGLE_pack_reverse_row_order GL_ANGLE_program_cache_control GL_ANGLE_provoking_vertex GL_ANGLE_request_extension GL_ANGLE_robust_client_memory GL_ANGLE_texture_compression_dxt3 GL_ANGLE_texture_compression_dxt5 GL_ANGLE_texture_multisample GL_ANGLE_texture_usage GL_ANGLE_translated_shader_source GL_CHROMIUM_bind_generates_resource GL_CHROMIUM_bind_uniform_location GL_CHROMIUM_copy_compressed_texture GL_CHROMIUM_copy_texture GL_CHROMIUM_lose_context GL_CHROMIUM_sync_query GL_EXT_EGL_image_external_wrap_modes GL_EXT_base_instance GL_EXT_blend_func_extended GL_EXT_blend_minmax GL_EXT_clip_control GL_EXT_color_buffer_float GL_EXT_color_buffer_half_float GL_EXT_debug_label GL_EXT_debug_marker GL_EXT_discard_framebuffer GL_EXT_disjoint_timer_query GL_EXT_draw_buffers GL_EXT_draw_buffers_indexed GL_EXT_draw_elements_base_vertex GL_EXT_float_blend GL_EXT_frag_depth GL_EXT_instanced_arrays GL_EXT_map_buffer_range GL_EXT_multi_draw_indi