When Thunderbird stuck on sending messages, it is caused by wrong server settings, incorrect password, a large attachment, antivirus issue, or a corrupted mail folder. The one quick fix is to check if you are not in offline mode (Alt + F > Offline). If this fails to resolve the issue, check your server settings or reduce the file or attachment size.

This guide why this issue occurs and gives you every possible solution to fix it with detailed step-by-step guide.

Table of Contents

Why Is Thunderbird Stuck On Sending Message?

When you send an email through Thunderbird, it connects to the outgoing server (usually SMTP), logs in and uploads the message for further process to continue. It saves a copy of that email in the folder labelled as Sent. If during this process any step fails or gets interrupted, Thunderbird gets stuck on sending messages. Here are some common issues to look upon.

  • Incorrect SMTP Server Settings

The wrong server name, port, or security issues stops Thunderbird from sending emails. This shows you “Sending of the message failed” error as the interruption in outgoing server settings triggers Thunderbird.

  • Expired or Wrong Password

If your Thunderbird password is changed or it saved an old one, the server often rejects the sign in and the message does not get sent.

  • Large Attachments in a Message

Most email providers allows limited file size transfer through email . A large attachment can hang or interrupt Thunderbird from sending emails as the upload may get slow or refused.

  • Security Software Blocks

Security software like Antivirus and Firewall scans the outgoing mails to protect your messages. This can block certain SMTP ports, resulting in Thunderbird not sending or loading messages.

  • Corrupted Sent Folder

A damaged Outbox stores old failed emails stuck in place and blocks new ones. A corrupted Sent folder can freeze the entire process at the final ‘copying message’ step.

How To Fix Thunderbird Stuck On Sending Message? 8 Step-by-Step Solutions

If you want to fix Thunderbird stuck on sending messages, here are some quick solutions that you can try–

Check Thunderbird Offline Mode and Your Internet Connection

If your Thunderbird is set to the Offline mode, messages are kept pending in the Outbox and does not get to send until you are in Online mode.

  1. Press Alt + F and in the drop down menu of File, select Offline.
  2. Check if the Work Offline is ticked or not. If ticked, change it to unticked.
  3. After that, check your internet connection and make sure it is active and stable.
  4. When both checked, go to File > Send Unsent Messages to retry sending pending emails.

Delete The Stuck Message From The Outbox

If any message fails or gets pending, it can block the queue. To resolve it–

  1. Open Outbox folder under Local Folders block.
  2. Select the emails that are stuck or pending, and click Delete.
  3. Then draft the message again.
  4. If the email does not get deleted, restart Thunderbird and try again.

Check Your Outgoing Server Settings

Before extensive settings change, verify your SMTP (Thunderbird outgoing server settings) first.

  1. From the menu (three horizontal lines), go to Account Settings > Outgoing Server (SMTP). Select the server and click Edit.
  2. Check port details (common value- 587) with STARTTLS or port 465 with SSL/TLS.
  3. Select the OAuth2 authentication method (in Google and Microsoft) and make sure you have written full email address.
  4. Incorrect settings or username are usually the main cause of Thunderbird not sending email message.

Re-enter Your Saved Password

  1. Open Settings from the menu and select Privacy & Security. Scroll to Passwords, and select Saved Passwords.
  2. Find your mail server from the list and select the entry and delete it by clicking on Remove.
  3. After that, you can restart Thunderbird and send email again.
  4. Enter your correct password when the prompt appears.

Also read: You can also export your emails in various formats using SysTools Thunderbird Converter.

Minimize Attachment Size

  1. If the email consists of large attachment files, try to send a short test message after removing them.
  2. Compress the attachment files in Zip format or save it on Google Drive or cloud and share the link instead of attachment.
  3. Thunderbird also has a feature named ‘Filelink’ feature, which can convert big attachments into links.

Check Security Software Settings

You can manage your Antivirus or Firewall settings and try sending the email again.

  1. Open your antivirus software settings.
  2. In settings, find email protection > mail shield or email Scanning setting.
  3. You can pause it for temporary timeline (10-15 minutes).
  4. Go back to Thunderbird and send a demo email.
  5. Check if it resolves your problem and the email is sent successfully.
  6. If it resolves, Keep Thunderbird in the exception list of your antivirus software.

Repair The Sent Folder

  1. In the side bar, right-click Sent folder.
  2. Select Properties > Repair Folder > OK.
  3. Now, wait for the folder to refresh as large folders can take a few minutes.

Note- Before repairing folder or deleting anything, always backup Thunderbird emails to ensure your emails are kept saved locally.

Update And Troubleshoot Mode

Your Thunderbird can have bugs that interrupt sending and receiving of emails. Ensure you update the Thunderbird first before starting troubleshoot steps.

  1. From the menu list (three lines) and go to Help > About Thunderbird.
  2. Wait a while till Thunderbird detects if any update is pending.
  3. If any update appears, click Restart to Update to complete it.
  4. After this, go back to Help > Troubleshoot Mode > Restart.
  5. Check if now you can send the file or it still hangs.

Remember– If nothing works out, create a new Thunderbird profile and re-add your account. This will resolve all your settings problem that were occurring in your previous profile.

Conclusion

To fix Thunderbird stuck on sending messages issue, start resolving it with the quickest fix to complex settings repair– check your internet connection, delete the stuck email, verify your server settings, check password, and try to reduce the attachment file size. If everything fails to resolve the problem, check your antivirus software settings and repair your folder or create a new profile.

FAQs

  1. Can I send an email from Thunderbird without saving it in the Sent folder?
    Yes. Choose Account Settings from the menu and click Copies & Folders, and unselect Place a copy in. This will avoid keeping copies of your mails in the sent folder.
  2. How is it possible that I am receiving emails in Thunderbird but not able to send any?
    Receiving an email uses incoming servers such as IMAP or POP3, while sending one uses outgoing SMTP server. One can work well while other can be failed due to some bug or settings fault.
  3. Can I schedule an email in Thunderbird instead of sending it ?
    Yes. You can schedule your email in Thunderbird using ‘Send Later 3’ add-on, but not with its built-in features. Thunderbird while scheduling email for later must be open and in online mode at the time for the message to send.
  4. Can I reinstall Thunderbird to fix Thunderbird stuck on sending message issue?
    Not really. A re-installation only resolves the problem that is inside the program itself. Your folders, settings, and profile stays same in place when you reinstall.