Create an app password for the POP server. https://help.yahoo.com/kb/grant-temporary-access-outdated-apps-account-settings-sln27791.html

For SMTP set the Authentication type to OAuth2 in your Thunderbird Account Settings for the Yahoo account.

Thank you, I generated the PW but not sure how to associate it to the POP in TBird. I was asked to name it then apply to app. Do I edit in PWMgr and replace my current PW?

Thanks again, Ken

Delete the current password in Thunderbird. Thunderbird will then prompt you for the new password when checking for new mail.

I can now receive emails...thank you. The only way I could remove the old PW in PWMgr was to remove the entire smtp://smtp.mail.yahoo.com line for my account. I checked the "save to PWMgr" box when prompted for the new PW so the mailbox://pop.mail.yahoo.com has been restored. I tried to send an email but another server error. How do I restore the smtp back to PWMgr. Sorry for the trouble. I wish one of the grandkids was here now to assist :)

Thank you, Ken

I tried to send an email but another server error.

What is the error exactly?

Did you adjust the Authentication type for the SMTP server as suggested above? https://support.mozilla.org/en-US/questions/1279357#answer-1288463

Here's the error: An error occurred while sending mail. The mail server responded: Request failed; Mailbox unavailable. Please verify that your email address is correct in your account settings and try again.

I'm guessing I should have set my smtp to OAuth2 first but I didn't, my bad. Now I only have the option to change with the other 2 accounts but not mine. As mentioned I have no smtp entry for my account in PWMgr, only the mailbox with the new PW which was added automatically. If you could provide me a detailed link to restore the smtp for my account I'll give it a go. Thank you for your patience. Ken

The mail server responded: Request failed; Mailbox unavailable.

This sounds like a different error, and Thunderbird doesn't even get to the point prompting you for a password.

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.

Now I only have the option to change with the other 2 accounts but not mine.

I don't think I understand the point you're trying to make here. Can you be more specific?

Thank you for your help but I think I'm making things worse. I need to know how to get this "smtp://smtp.mail.yahoo.com (smtp://smtp.mail.yahoo.com)" back into the Pword Mgr for my account. I have "mailbox://pop.mail.yahoo.com (mailbox://pop.mail.yahoo.com)" now, with your help, so I am receiving emails but I'm guessing I need the smtp entry as I can't send. Perhaps the best thing might be my first thought of uninstalling then re-downloading Tbird, but if there's an easier way of getting it back in Pwmgr all the better. Thanks again, Ken

Perhaps the best thing might be my first thought of uninstalling then re-downloading Tbird

You'll be wasting your time. The problem is with your Thunderbird profile. Profile files are stored separately from the Thunderbird program files. The program files are static and do not change (except when you upgrade the Thunderbird application version). Because we store profile and program files separately, you can uninstall Thunderbird without losing your messages and settings, and if something goes wrong with a Thunderbird update your information will still be available. It also means that you don't have to reinstall Thunderbird in order to delete your information or troubleshoot a problem.

I need to know how to get this "smtp://smtp.mail.yahoo.com (smtp://smtp.mail.yahoo.com)" back into the Pword Mgr for my account.

As said before, please post your Troubleshooting Information.

Application Basics Name: Thunderbird

   Version: 68.5.0
   Build ID: 20200210021033

Update Channel: release

   User Agent: Mozilla/5.0 (Windows NT 10.0; WOW64; rv:68.0) Gecko/20100101 Thunderbird/68.5.0
   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, , (pop3) pop.mail.yahoo.com:995, SSL, passwordCleartext
     OUTGOING: , smtp.mail.yahoo.com:465, SSL, passwordCleartext, true

account2:

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

account3:

     INCOMING: account3, , (pop3) pop.mail.yahoo.com:995, SSL, passwordCleartext
     OUTGOING: , smtp.mail.yahoo.com:465, SSL, passwordCleartext, true
account4:
     INCOMING: account4, , (pop3) pop.mail.yahoo.com:995, SSL, passwordCleartext
     OUTGOING: , smtp.mail.yahoo.com:465, SSL, passwordCleartext, true

Crash Reports for the Last 3 Days Remote Processes

Type: Count

Extensions Name

     Version
     Enabled
     ID

Amazon.co.uk

       1.1
       true
       [email protected]

Bing

       1.0
       true
       [email protected]
DuckDuckGo
       1.0
       true
       [email protected]

Google

       1.0
       true
       [email protected]

Lightning

       68.5.0
       true
       {e2fda1a4-762b-4020-b5ad-a41df1933103}
Twitter
       1.0
       true
       [email protected]

       Wikipedia (en)
       1.0
       true
       [email protected]

 Security Software

   Type: Name

     Antivirus: AVG Antivirus
     Antispyware:
     Firewall: Windows Firewall

 Graphics

     Features
     Compositing: Basic
     Asynchronous Pan/Zoom: none
     WebGL 1 Driver WSI Info: EGL_VENDOR: Google Inc. (adapter LUID: 000000000000aa5d)

EGL_VERSION: 1.4 (ANGLE 2.1.0.8a050090f926) 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_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

     WebGL 1 Driver Renderer: Google Inc. -- ANGLE (AMD Radeon HD 6320 Graphics Direct3D11 vs_5_0 ps_5_0)
     WebGL 1 Driver Version: OpenGL ES 2.0 (ANGLE 2.1.0.8a050090f926)
     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_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_compressed_ETC1_RGB8_texture 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_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_disjoint_timer_query EXT_float_blend EXT_frag_depth EXT_shader_texture_lod EXT_sRGB EXT_texture_compression_bptc EXT_texture_filter_anisotropic 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: 000000000000aa5d)

EGL_VERSION: 1.4 (ANGLE 2.1.0.8a050090f926) 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_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

     WebGL 2 Driver Renderer: Google Inc. -- ANGLE (AMD Radeon HD 6320 Graphics Direct3D11 vs_5_0 ps_5_0)
     WebGL 2 Driver Version: OpenGL ES 3.0 (ANGLE 2.1.0.8a050090f926)
     WebGL 2 Driver Extensions: GL_ANGLE_client_arrays GL_ANGLE_copy_texture_3d 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_multisample 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_sync_query GL_EXT_blend_func_extended GL_EXT_blend_minmax GL_EXT_color_buffer_float 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_filt

Try to start Windows in safe mode with networking enabled. - Win10 https://support.microsoft.com/en-us/help/12376/windows-10-start-your-pc-in-safe-mode

Still in Windows safe mode, start Thunderbird in safe mode. - https://support.mozilla.org/kb/safe-mode

Does the problem go away?

Unfortunately no, I still cannot send and get the same error:

An error occurred while sending mail. The mail server responded: Request failed; Mailbox unavailable. Please verify that your email address is correct in your account settings and try again.

Thank you, Ken

Can you confirm you did start Windows in safe mode?

Double-check the spelling of your email address. Is it correct?

From your Troubleshooting Information, you still didn't change the Authentication type for the SMTP server as advised earlier. https://support.mozilla.org/en-US/questions/1279357#answer-1288463

Yes to questions 1&2. As I mentioned previously I cannot access the change smtp for my account when I open edit smtp server. For the other 2 accounts the corresponding addresses are in the user name field but it's one of the other addresses showing when when I open in mine. From 10-02 "The only way I could remove the old PW in PWMgr was to remove the entire smtp://smtp.mail.yahoo.com line for my account."

This must be the root of my problem, self inflicted no doubt. As I posted earlier, in PWmgr I have two lines for both functioning accounts....mailbox pop and SMTP but only the mailbox pop for mine.

Obviously I shouldn't have deleted the entire line but I saw no other option at the time....mea culpa. If it's not a resolvable issue I understand. Thank you, Ken

I cannot access the change smtp for my account when I open edit smtp server.

And what exactly prevents you from doing that?

"The only way I could remove the old PW in PWMgr was to remove the entire smtp://smtp.mail.yahoo.com line for my account." This must be the root of my problem

No, it's not.

For the other 2 accounts the corresponding addresses are in the user name field but it's one of the other addresses showing when when I open in mine.

Sounds like this is your problem.