Thunderbird users often find it difficult to send or receive emails because the settings they are using are incorrect. You can refer to the steps below to review the settings and fix the problem:
• Step 1: Go to the Account Settings and review your SMTP outgoing email settings and then try and send your emails again.
• Step 2: Go to the Firewall settings on your PC and ensure your outgoing email is not being blocked.
• Step 3: Switch off your antivirus software and disabling the firewall before sending out an email using Thunderbird.
If you find that you still encounter email errors even after you implement the steps mentioned above you can call the Mozilla Thunderbird support number and ask for help. Read more for: https://www.contact-emails.com/mozilla-thunderbird/