Assuming the mail server set in TB to send emails is not Gmail then you might try this as on TB v78 the minimum requirement for SSL has increased and probably your email service provider still uses deprecated security for the mail server. You can try to set lowest security by following the below steps and let us know how it works...

From the menu at the top right, go to Options. Scroll all the way to the bottom and click on Config Editor -> Skip past the warning. Scroll down until you find security.tls.version.min (or paste security.tls.version.min to upper frame) Change the value 3 to 2. Restart TB. If it's still not working then change the same option again but this time to 1. Restart TB. If still doesn't work try to set also security.tls.version.enable-deprecated = true

they ARE gmail. given your first statement, I haven't tried this. should I?

they ARE gmail. given your first statement, I haven't tried this. should I?

No, you shouldn't mess with security settings in about:config.

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

Name: Thunderbird

   Version: 78.2.2
   Build ID: 20200908210243
   Distribution ID:

   Update Channel: release
   User Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:78.0) Gecko/20100101 Thunderbird/78.2.2
   OS: Windows_NT 10.0

   Launcher Process: Enabled
   Multiprocess Windows: 0/0
             Disabled
   Remote Processes: 0
   Enterprise Policies: Inactive
   Google Location Service Key: Missing
   Google Safebrowsing Key: Missing
   Mozilla Location Service Key: Missing
   Safe Mode: false

 Mail and News Accounts
   account1:
     INCOMING: account1, , (none) Local Folders, plain, passwordCleartext

   account5:
     INCOMING: account5, , (pop3) imap.googlemail.com:1, SSL, passwordCleartext
     OUTGOING: , smtp.gmail.com:587, SSL, passwordCleartext, true

   account6:
     INCOMING: account6, , (pop3) imap.googlemail.com:110, SSL, passwordCleartext
     OUTGOING: , smtp.gmail.com:587, SSL, passwordCleartext, true

   account7:
     INCOMING: account7, , (pop3) pop.gmail.com:110, plain, passwordCleartext
     OUTGOING: , smtp.gmail.com:587, SSL, passwordCleartext, true

   account8:
     INCOMING: account8, , (imap) imap.googlemail.com:110, SSL, passwordCleartext
     OUTGOING: , smtp.gmail.com:587, SSL, passwordCleartext, true

   account9:
     INCOMING: account9, , (pop3) pop.googlemail.com:995, SSL, passwordCleartext
     OUTGOING: , smtp.googlemail.com:465, SSL, passwordCleartext, true

   account10:
     INCOMING: account10, , (pop3) pop.googlemail.com:995, SSL, passwordCleartext
     OUTGOING: , smtp.gmail.com:465, SSL, passwordCleartext, true

   account11:
     INCOMING: account11, , (pop3) pop.googlemail.com:995, SSL, passwordCleartext
     OUTGOING: , smtp.googlemail.com:465, SSL, passwordCleartext, true

   account12:
     INCOMING: account12, , (imap) imap.gmail.com:993, SSL, OAuth2
     OUTGOING: , smtp.gmail.com:587, alwaysSTARTTLS, OAuth2, true

   account13:
     INCOMING: account13, , (pop3) pop.gmail.com:995, SSL, passwordCleartext
     OUTGOING: , smtp.gmail.com:465, SSL, OAuth2, true

 Crash Reports for the Last 3 Days

 Remote Processes

   Type: Count

 Extensions

     Name
     Version
     Enabled
     ID

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

       Bing
       1.0
       true
       bing@search.mozilla.org

       DuckDuckGo
       1.0
       true
       ddg@search.mozilla.org

       Google
       1.0
       true
       google@search.mozilla.org

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

 Security Software

   Type: Name

     Antivirus: ESET Security
     Antispyware:
     Firewall: Windows Firewall

 Graphics

     Features
     Compositing: Direct3D 11 (Advanced Layers)
     Asynchronous Pan/Zoom: none
     WebGL 1 Driver WSI Info: EGL_VENDOR: Google Inc. (adapter LUID: 0000000000008e8f)

EGL_VERSION: 1.4 (ANGLE 2.1.0.6c72b64f910d) 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_NV_post_sub_buffer EGL_KHR_create_context EGL_EXT_device_query 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_flexible_surface_compatibility 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_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_EXTENSIONS(nullptr): EGL_EXT_client_extensions EGL_EXT_platform_base EGL_EXT_platform_device EGL_ANGLE_platform_angle EGL_ANGLE_platform_angle_d3d 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_explicit_context EGL_ANGLE_feature_control

     WebGL 1 Driver Renderer: Google Inc. -- ANGLE (Intel(R) HD Graphics Direct3D11 vs_5_0 ps_5_0)
     WebGL 1 Driver Version: OpenGL ES 2.0.0 (ANGLE 2.1.0.6c72b64f910d)
     WebGL 1 Driver Extensions: GL_ANGLE_client_arrays GL_ANGLE_depth_texture GL_ANGLE_explicit_context GL_ANGLE_explicit_context_gles1 GL_ANGLE_framebuffer_blit GL_ANGLE_framebuffer_multisample 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_usage GL_ANGLE_translated_shader_source GL_CHROMIUM_bind_generates_resource GL_CHROMIUM_bind_uniform_location GL_CHROMIUM_color_buffer_float_rgb GL_CHROMIUM_color_buffer_float_rgba GL_CHROMIUM_copy_compressed_texture GL_CHROMIUM_copy_texture GL_CHROMIUM_lose_context GL_CHROMIUM_sync_query GL_EXT_blend_func_extended GL_EXT_blend_minmax GL_EXT_color_buffer_half_float GL_EXT_debug_marker GL_EXT_discard_framebuffer GL_EXT_disjoint_timer_query GL_EXT_draw_buffers GL_EXT_float_blend GL_EXT_frag_depth GL_EXT_instanced_arrays GL_EXT_map_buffer_range GL_EXT_occlusion_query_boolean GL_EXT_read_format_bgra GL_EXT_robustness GL_EXT_sRGB GL_EXT_shader_texture_lod GL_EXT_texture_compression_bptc GL_EXT_texture_compression_dxt1 GL_EXT_texture_compression_s3tc_srgb GL_EXT_texture_filter_anisotropic GL_EXT_texture_format_BGRA8888 GL_EXT_texture_rg GL_EXT_texture_storage GL_EXT_unpack_subimage GL_KHR_debug GL_KHR_parallel_shader_compile GL_KHR_robust_buffer_access_behavior GL_NV_EGL_stream_consumer_external GL_NV_fence GL_NV_pack_subimage GL_NV_pixel_buffer_object GL_OES_EGL_image GL_OES_EGL_image_external GL_OES_depth24 GL_OES_depth32 GL_OES_element_index_uint GL_OES_get_program_binary GL_OES_mapbuffer GL_OES_packed_depth_stencil GL_OES_rgb8_rgba8 GL_OES_standard_derivatives GL_OES_surfaceless_context GL_OES_texture_3D GL_OES_texture_border_clamp GL_OES_texture_float GL_OES_texture_float_linear GL_OES_texture_half_float GL_OES_texture_half_float_linear GL_OES_texture_npot GL_OES_vertex_array_object OES_compressed_EAC_R11_signed_texture OES_compressed_EAC_R11_unsigned_texture OES_compressed_EAC_RG11_signed_texture OES_compressed_EAC_RG11_unsigned_texture OES_compressed_ETC2_RGB8_texture OES_compressed_ETC2_RGBA8_texture OES_compressed_ETC2_punchthroughA_RGBA8_texture OES_compressed_ETC2_punchthroughA_sRGB8_alpha_texture OES_compressed_ETC2_sRGB8_alpha8_texture OES_compressed_ETC2_sRGB8_texture
     WebGL 1 Extensions: ANGLE_instanced_arrays EXT_blend_minmax EXT_color_buffer_half_float EXT_float_blend EXT_frag_depth EXT_shader_texture_lod EXT_sRGB EXT_texture_compression_bptc EXT_texture_filter_anisotropic MOZ_debug OES_element_index_uint OES_standard_derivatives OES_texture_float OES_texture_float_linear OES_texture_half_float OES_texture_half_float_linear OES_vertex_array_object WEBGL_color_buffer_float WEBGL_compressed_texture_s3tc WEBGL_compressed_texture_s3tc_srgb WEBGL_debug_renderer_info WEBGL_debug_shaders WEBGL_depth_texture WEBGL_draw_buffers WEBGL_lose_context
     WebGL 2 Driver WSI Info: EGL_VENDOR: Google Inc. (adapter LUID: 0000000000008e8f)

EGL_VERSION: 1.4 (ANGLE 2.1.0.6c72b64f910d) 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_NV_post_sub_buffer EGL_KHR_create_context EGL_EXT_device_query 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_flexible_surface_compatibility 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_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_EXTENSIONS(nullptr): EGL_EXT_client_extensions EGL_EXT_platform_base EGL_EXT_platform_device EGL_ANGLE_platform_angle EGL_ANGLE_platform_angle_d3d 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_explicit_context EGL_ANGLE_feature_control

     WebGL 2 Driver Renderer: Goog

thanks, it had too many characters so I deleted some of the emails that are not involved, but not all of them. pretty sure it's the account 9, 10 and 11

oh, the email you requested is being monitored. hopefully it will appear and you can help me. very appreciative

Just copying the 'Mail and News Accounts' section will do. In any case, you'd also need to paste the copied information into your reply.

Mail and News Accounts ID Incoming server Outgoing servers Name Connection security Authentication method Name Connection security Authentication method Default? account1 (none) Local Folders None Normal password account2 (pop3) pop.easystreet.com:110 None Normal password smtp.gmail.com:587 SSL/TLS Normal password true account3 (pop3) pop.easystreet.com:110 None Normal password smtp.gmail.com:587 SSL/TLS Normal password true account4 (pop3) pop.easystreet.com:110 None Normal password smtp.gmail.com:587 SSL/TLS Normal password true account5 (pop3) imap.googlemail.com:1 SSL/TLS Normal password smtp.gmail.com:587 SSL/TLS Normal password true account6 (pop3) imap.googlemail.com:110 SSL/TLS Normal password smtp.gmail.com:587 SSL/TLS Normal password true account7 (pop3) pop.gmail.com:110 None Normal password smtp.gmail.com:587 SSL/TLS Normal password true account8 (imap) imap.googlemail.com:110 SSL/TLS Normal password smtp.gmail.com:587 SSL/TLS Normal password true account9 (pop3) pop.googlemail.com:995 SSL/TLS Normal password smtp.googlemail.com:465 SSL/TLS Normal password true account10 (pop3) pop.googlemail.com:995 SSL/TLS Normal password smtp.gmail.com:465 SSL/TLS Normal password true account11 (pop3) pop.googlemail.com:995 SSL/TLS Normal password smtp.googlemail.com:465 SSL/TLS Normal password true account12 (imap) imap.gmail.com:993 SSL/TLS OAuth2 smtp.gmail.com:587 STARTTLS OAuth2 true account13 (pop3) pop.gmail.com:995 SSL/TLS Normal password smtp.gmail.com:465 SSL/TLS OAuth2 true

it is only accounts 9, 10 & 11

gone to monitoring again.

gone to monitoring again.

What does this mean?

account9 (pop3) pop.googlemail.com:995 SSL/TLS Normal password smtp.googlemail.com:465 SSL/TLS Normal password true

All your accounts are POP and use 'Normal password' authentication. That means you'll have to 'allow less secure apps' in your Google settings (not Thunderbird) for your Google account(s). https://support.google.com/accounts/answer/6010255?hl=en

Alternatively you can change the account settings for your Gmail account(s) in Thunderbird as follows: At the top right of the Thunderbird window, click the menu button > Options > Account Settings Instead of 'Normal password' authentication change the authentication type to 'OAuth2' for both, the incoming server (POP), as well as for the outgoing server (SMTP) for your Gmail account(s). Then you don't need to 'allow less secure apps' anymore in your Google settings.

Security Software Type: Name Antivirus: ESET Security

These are some generic suggestions to avoid problems with anti-virus software.

Create an exception in your anti-virus software for the Thunderbird profile folder, so that the anti-virus real-time scanner will not scan it. http://kb.mozillazine.org/Profile_folder_-_Thunderbird

Don't let your anti-virus software scan incoming and outgoing messages.

Don't let your anti-virus software scan attachments.

Don't let your anti-virus software intercept your secure connection to the server.

Remove any add-ons your anti-virus software may have installed in Thunderbird.

I am already allowing less secure apps in Google-- since the last time this happened. that's what got me so confused and stymied this time

I did the change from Normal to OAuth2. I only found one place to change it under just one heading Security Settings. my choices on that first line Security Settings are none, ssl/tls and starttes. it is set at ssl/tls

nothing changed. entered my password again but that didn't help. Got this message:

Sending of the message failed. Failed due to unexpected error 80004005. No description is available. The message could not be sent using Outgoing server (SMTP) smtp.googlemail.com for an unknown reason. Please verify that your Outgoing server (SMTP) settings are correct and try again.

I so appreciate your efforts on my behalf!

I thought I already typed the following but not seeing it so repeating

I tried changing to Normal but it only had one place to change it under Security Settings where it offered 3 choices: SSL/TLS, NONE, STARTTLS I didnt' change that. it is SSL/TLS

I changed the authentification to OAuth2 but it's still the same. got this message again after entering my password when they asked

Sending of the message failed. Failed due to unexpected error 80004005. No description is available. The message could not be sent using Outgoing server (SMTP) smtp.googlemail.com for an unknown reason. Please verify that your Outgoing server (SMTP) settings are correct and try again.

shortly after Google asked me to sign into that account again.

On accounts 9/10/11 you have port 465 while for rest of them you have port 587 Can you try to change that info to 587 for those accounts and see if there is any difference?

thanks but, sadly, the one that is working is 13 and it is set exactly like the ones that aren't. most of the accounts above are old ones I don't use and I only keep for their archives.

OK, but then 9/10/11 are SSL/TLS Normal password true while 13 is SSL/TLS OAuth2 true... Can you try to change then 9/10/11 to OAuth2?

the one that is working is 13 and it is set exactly like the ones that aren't.

No it's not. Account13 is set up properly with OAuth2 authentication, while 9-11 are not. To change them to OAuth2 authentication has been suggested before, but for some reason you choose not to follow the suggestion: https://support.mozilla.org/en-US/questions/1306065#answer-1353532

I did follow your advise but it didn't make any difference. please look above at what I wrote at 2:17pm yesterday. since it didn't work, I changed it back.

I'm going to try downloading Thunderbird again and see if that helps

Solved! you were correct Chris. I was unable to find the outgoing server settings yesterday. finally I did and it worked after redownloading Thunderbird. Thank you SO MUCH and apologies for my ignorance but then that's why I needed help and I am very grateful!!!!