I can send no emails. Some emails that show in the inbox show a blank screen and can not be deleted. All messages I send come back with an end of message error and SMTP blocked (see attached).

First of all, make sure you do have a backup of your Thunderbird profile. https://support.mozilla.org/en-US/kb/profiles-where-thunderbird-stores-user-data#w_backing-up-a-profile

Chances are that Bitdefender is messing things up. Therefore create an exception in Bitdefender for the Thunderbird profile folder, so that the Bitdefender real-time scanner will not scan it. https://support.mozilla.org/en-US/kb/profiles-where-thunderbird-stores-user-data#w_how-to-find-your-profile

Once done that you can try to fix Inbox. Right-click Inbox in the folder pane - Properties - Repair Folder

No matter what I do or what I deleteincluding shutdown after every delete, when I reinstall it comes back with the total and Faulty Thunderbird

You can reinstall the application as many times as you want, it won't change a thing. All your data such as messages, passwords and user preferences, and changes made while you use Thunderbird, are stored in a special folder called a profile. Your profile folder is stored in a separate place from the Thunderbird program, so that if something ever goes wrong with Thunderbird your information will still be there. It also means that you can uninstall Thunderbird and reinstall without losing your settings and data.

If none of the above fixes the problems, you can still try to create a new profile, and start from scratch. https://support.mozilla.org/en-US/kb/using-multiple-profiles

Thank you for that. Firstly, inbox problem solved, thanks for that. Secondly, I had saved a copy by using export to a .zip file in Documents. Thirdly, there are two files in profiles denisxxxx and defaultxxxx so I created a bitdefender exception for both. No chage unfortunately, still get the end of message, SMTP blocked when I try to send or rply to emails. If I use multple profiles will this still keep the original and is the new profile likely to bypass the SMTP port 587 error do you think?

still get the end of message, SMTP blocked when I try to send or rply to emails.

Try to start Windows 10 in safe mode with networking enabled. Still in Windows safe mode, start Thunderbird in safe mode. Does the problem go away?

Windows safe mode disables anti-virus software. This is a troubleshooting step, not a solution.

If I use multple profiles will this still keep the original

Yes, it will. And you do have multiple profiles already, don't you. Having said that, make sure you do have recent profile backups though.

is the new profile likely to bypass the SMTP port 587 error do you think?

I don't know. What is your email provider? And what are the server settings required by your email provider?

Also, 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.

Too many characters message when I try to post that. It's 365 too many. Can anything be cut?

Just tried safe mode, result is exactly the same.

Too many characters message when I try to post that. It's 365 too many. Can anything be cut?

You can either split it into smaller batches, or cut from the bottom.

Just tried safe mode, result is exactly the same.

Can you confirm you did start Windows in safe mode?

Are you running a VPN?

The "SMTP blocked" part of the error message you get is unclear whether it means the SMTP server is blocking you or the incoming server of the recipient is blocking your SMTP server. The "Please check the message and try again" part, however, seems to indicate the problem is with the message itself and that your SMTP server is refusing to send it because there is something about your message that the SMTP server doesn't like.

It could be that your SMTP server has become more strict and now requires messages sent through it to be sent from the same email address that you use to authenticate to the server, for example. Do the messages giving you this error have a "From" address different from the username you use to authenticate with the SMTP server?

Part1

 Application Basics

   Name: Thunderbird
   Version: 128.6.0esr
   Build ID: 20250107005646
   Distribution ID:

   Update Channel: esr
   User Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:128.0) Gecko/20100101 Thunderbird/128.6.0
   OS: Windows_NT 10.0 19045
   OS Theme:

   Launcher Process: Enabled
   Multiprocess Windows: 0/0
   Fission Windows: 0/0
             Enabled by default
   Remote Processes: 2
   Enterprise Policies: Active
   Google Location Service Key: Missing
   Google Safebrowsing Key: Missing
   Mozilla Location Service Key: Missing
   Safe Mode: false
   Memory Size (RAM): 15.9 GB
   Disk Space Available: 73.6 GB

 Mail and News Accounts
   account1:
     INCOMING: account1, , (pop3) pop3.extendcp.co.uk:995, SSL, passwordCleartext
     OUTGOING: , mta.extendcp.co.uk:587, 2, passwordCleartext, true

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

   account8:
     INCOMING: account8, , (pop3) pop3.extendcp.co.uk:995, SSL, passwordCleartext
     OUTGOING: , mta.extendcp.co.uk:587, 2, passwordCleartext, true

   account16:
     INCOMING: account16, , (pop3) mail.plus.net:110, 0, passwordCleartext
     OUTGOING: , relay.plus.net:465, 2, passwordCleartext, true

   account17:
     INCOMING: account17, , (pop3) mail.plus.net:110, 0, passwordCleartext
     OUTGOING: , relay.plus.net:465, 2, passwordCleartext, true

   account27:
     INCOMING: account27, , (imap) imap.gmail.com:993, SSL, OAuth2
     OUTGOING: , smtp.gmail.com:465, SSL, OAuth2, true

   account28:
     INCOMING: account28, , (pop3) pop3.extendcp.co.uk:995, SSL, passwordCleartext
     OUTGOING: , mta.extendcp.co.uk:587, 2, passwordCleartext, true

 Libraries

     Library
     Status
     Expected minimum version
     Version in use
     Path

       RNP (OpenPGP)
       OK
       0.17.1
       0.17.1.MZLA.128.6.0esr.botan
       C:\Program Files\Mozilla Thunderbird\rnp.dll

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

 Calendar Settings

     Formula 1

       Name
       Value

       Name:
       Type: caldav
       Disabled: false
       Username:
       URI:
       Refresh Interval: 30
       Read-only: false
       Suppress Alarms: false
       Cache Enabled: true
       iMIP Identity: id1
       iMIP Disabled:
       iMIP Account:
       Organiser Id:
       Force Email Scheduling: false
       Popup Alarms Supported:
       Alarms on Invitation Supported:
       Max Alarms Per Event:
       Attachment Supported:
       Max Categories:
       Privacy State Supported:
       Priority Supported:
       Event Supported: true
       Task Supported: false
       Local Time Supported:
       UTC/GMT Supported:
       Auto-Scheduling Supported: true

     Birthdays

       Name
       Value

       Name:
       Type: caldav
       Disabled: false
       Username:
       URI:
       Refresh Interval: 30
       Read-only: false
       Suppress Alarms: false
       Cache Enabled: true
       iMIP Identity: id1
       iMIP Disabled:
       iMIP Account:
       Organiser Id:
       Force Email Scheduling: false
       Popup Alarms Supported:
       Alarms on Invitation Supported:
       Max Alarms Per Event:
       Attachment Supported:
       Max Categories:
       Privacy State Supported:
       Priority Supported:
       Event Supported: true
       Task Supported: false
       Local Time Supported:
       UTC/GMT Supported:
       Auto-Scheduling Supported: true

     Holidays in United Kingdom

       Name
       Value

       Name:
       Type: caldav
       Disabled: false
       Username:
       URI:
       Refresh Interval: 30
       Read-only: false
       Suppress Alarms: false
       Cache Enabled: true
       iMIP Identity: id1
       iMIP Disabled:
       iMIP Account:
       Organiser Id:
       Force Email Scheduling: false
       Popup Alarms Supported:
       Alarms on Invitation Supported:
       Max Alarms Per Event:
       Attachment Supported:
       Max Categories:
       Privacy State Supported:
       Priority Supported:
       Event Supported: true
       Task Supported: false
       Local Time Supported:
       UTC/GMT Supported:
       Auto-Scheduling Supported: true

     denis.greenough@gmail.com

       Name
       Value

       Name:
       Type: caldav
       Disabled: false
       Username:
       URI:
       Refresh Interval: 30
       Read-only: false
       Suppress Alarms: false
       Cache Enabled: true
       iMIP Identity: id1
       iMIP Disabled:
       iMIP Account:
       Organiser Id:
       Force Email Scheduling: false
       Popup Alarms Supported:
       Alarms on Invitation Supported:
       Max Alarms Per Event:
       Attachment Supported:
       Max Categories:
       Privacy State Supported:
       Priority Supported:
       Event Supported: true
       Task Supported: false
       Local Time Supported:
       UTC/GMT Supported:
       Auto-Scheduling Supported: true

Part 2

Home

       Name
       Value

       Name:
       Type: storage
       Disabled:
       Username:
       URI:
       Refresh Interval:
       Read-only:
       Suppress Alarms:
       Cache Enabled:
       iMIP Identity: id1
       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

     GPU: 1
     Extension: 1

 Add-ons

     Name
     Type
     Version
     Enabled
     ID

       British English Dictionary (Marco Pinto)
       dictionary
       3.3.7
       true
       marcoagpinto@mail.telepac.pt

       Addon Compatibility Check
       extension
       1.10.10
       true
       addoncompatibility@opto.one

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

       Bing
       extension
       1.0
       true
       bing@search.mozilla.org

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

       DuckDuckGo
       extension
       1.0
       true
       ddg@search.mozilla.org

       Google
       extension
       1.0
       true
       google@search.mozilla.org

       Old Icons
       extension
       1.6
       true
       oldicons@deltablast

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

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

       Bitdefender Toolbar
       extension
       27.0.40.173
       false
       bdThunderbird111@bitdefender.com

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

       NoGlass
       theme
       0.12
       false
       noglass@paenglab.ch

       Nuvola
       theme
       1.48
       false
       NuvolaTB@paenglab.ch

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

       xpDefault
       theme
       52.1.3
       false
       xpDefault@mikk.cz

 Security Software

   Type: Name

     Antivirus: Bitdefender Antivirus
     Antispyware:
     Firewall: Bitdefender 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; 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

christ1 Safe mode + network.

No VPN.

Troubleshooting Information shows multiple accounts. Which is the one with the SMTP problem?

Safe mode + network.

While running Windows in safe mode, did you also start Thunderbird in safe mode?

The "SMTP blocked" part of the error message you get is unclear whether it means the SMTP server is blocking you or the incoming server of the recipient is blocking your SMTP server. The "Please check the message and try again" part, however, seems to indicate the problem is with the message itself and that your SMTP server is refusing to send it because there is something about your message that the SMTP server doesn't like.

Agreed.

It could be that your SMTP server has become more strict and now requires messages sent through it to be sent from the same email address that you use to authenticate to the server, for example. Do the messages giving you this error have a "From" address different from the username you use to authenticate with the SMTP server?

Not sure what you mean there. Example: I post from "joe@joebloggs.co.uk" among others which are all "xfilename@joebloggs.co.uk". They are all hosted under "joebloggs.co.uk", my own IP address, not that actual one obviously. What do I need to look at as your post is interesting.

Troubleshooting Information shows multiple accounts. Which is the one with the SMTP problem?

Safe mode + network.

While running Windows in safe mode, did you also start Thunderbird in safe mode?

Yes, unless there is an alternate way of starting Thunderbird in its own safe mode?

Sorry christ1 I should have added all posts from @denisg.co.uk. That's denis, ebay and elite.

You need to authenticate with the outgoing server for sending messages just like you need to authenticate with the incoming server in order to receive them. The most common way to do that is with a username and password that the mail client stores so you don't have to type them every time. The username is usually the full email address or the part of the email address preceding the '@' sign associated with the mail account. You may check what username you're using for the SMTP server in you Outgoing Server (SMTP) settings. Check the screenshot in the following help article if you have trouble finding that:

https://support.mozilla.org/kb/cannot-send-messages

Your SMTP server could now be requiring that the "From" address of your messages be the same as the email address used as the account username, and refuse to send your messages if you don't do that.

Troubleshooting Information shows multiple accounts. Which is the one with the SMTP problem?

For the others, Plusnet and gmail I use their server details. No problem. I have test emailed from these to my home address and have been sent and received OK. The host for my email a/c is british and they say that they have tested from all my email addresses using their own app and they found no problem.

You need to authenticate with the outgoing server for sending messages just like you need to authenticate with the incoming server in order to receive them. The most common way to do that is with a username and password that the mail client stores so you don't have to type them every time. The username is usually the full email address or the part of the email address preceding the '@' sign associated with the mail account. You may check what username you're using for the SMTP server in you Outgoing Server (SMTP) settings. Check the screenshot in the following help article if you have trouble finding that: https://support.mozilla.org/kb/cannot-send-messages Your SMTP server could now be requiring that the "From" address of your messages be the same as the email address used as the account username, and refuse to send your messages if you don't do that.

I get that, see attachments

Right, now try sending a message from that address and see whether you still get the same error.

Right, now try sending a message from that address and see whether you still get the same error.

Yes. With respect, that is the problem.

OK, but nowhere did you say until now that was the problem. In fact, you seemed to say in a previous post that you were sending from multiple addresses, all associated with the same account, but not necessarily any of them the same as the one used for the username, so there was the possibility that that could be the problem.