Thunderbird Sending of the Message Failed

Important Tips to Follow

• Verify the SMTP server, port, authentication, and connection security settings before changing your Thunderbird profile.
• Make sure your internet connection is stable.
• Check whether your email provider has any temporary service issues.
• Keep attachments within your provider's allowed size limit.
• Create a backup of your Thunderbird profile before making major changes.
• Do not delete the existing Thunderbird profile until you have confirmed that your mailbox data is safely accessible.
• If the issue continues after SMTP troubleshooting, consider testing the account in another email client to determine whether the problem is specific to Thunderbird.
• If you need to move or re-import local mailbox data, use a dedicated import solution rather than repeatedly modifying the original profile.

Conclusion

The “Sending of the message failed” error in Thunderbird can occur because of incorrect SMTP settings, authentication problems, firewall or antivirus interference, attachment issues, or problems with the local Thunderbird profile. Start with the basic SMTP and account checks before making changes to your profile.

If the problem is connected to managing or importing local mailbox data, provides a professional way to import MBOX files into Thunderbird profiles without relying entirely on the application's manual import process. This can be particularly useful when dealing with profile migration or local mailbox management.