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Outgoing Email Suddenly Stopped Working upon Thunderbird Upgrade due to "Unknown Error"

  • 2 replies
  • 1 has this problem
  • 11 views
  • Last reply by kmorgan1

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Hello, I have seen several forum posts about this same thing and nothing in any of them has solved the problem.

My Thunderbird email has been working fine until yesterday, when I started to get this message:

"The message could not be sent using Outgoing server (SMTP) for an unknown reason. Please verify that your Outgoing server (SMTP) settings are correct and try again."

I had not changed any settings or done anything differently. The only difference is that I had upgraded Thunderbird to version 91.4.0 the day before.

I have tried everything recommended in the forums I have read and nothing is working.

If there is no solution, is it possible to downgrade back to the previous version?

Hello, I have seen several forum posts about this same thing and nothing in any of them has solved the problem. My Thunderbird email has been working fine until yesterday, when I started to get this message: "The message could not be sent using Outgoing server (SMTP) for an unknown reason. Please verify that your Outgoing server (SMTP) settings are correct and try again." I had not changed any settings or done anything differently. The only difference is that I had upgraded Thunderbird to version 91.4.0 the day before. I have tried everything recommended in the forums I have read and nothing is working. If there is no solution, is it possible to downgrade back to the previous version?

All Replies (2)

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What mail provider is the issue with? yahoo, AOL have recently changed server settings and google has enforced oauth or two factor authentication.

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Hi Matt, your answer provided me with a clue, thank you! My email is hosted with Digital Space, so I called their support and they verified that indeed, they had a problem with their outgoing servers over the past couple of days. Their server issue was resolved, and they "reset" (whatever that means) my email address, and voila! outgoing mail is functional again.

But then I discovered a further issue, if I tried to send email with my normal HTML signature block (has my name and graphics that link out to my website), it would error out again. As long as I don't include the signature block, it works fine. Not sure what that means, but for now I won't be using my signature block until it can be re-coded to see if that fixes it.

Thank you again for your response, and I hope this helps anyone else who may have the same problem.

Modified by kmorgan1