To change an email password, go to the email provider site to do that, and then when you check mail again, Thunderbird will be prompted to provide the new password and you can enter it then.

I would love an answer to this, but can't get my emails, so guess it won't help much

Did not work

To change an email password, go to the email provider site to do that, and then when you check mail again, Thunderbird will be prompted to provide the new password and you can enter it then.

I have already done this and it still won't send. I can receive but not send.

I have already done what you suggested (it's the first thing I did) and it still won't send. I can receive but not send.

Maybe if you post screenshot of your incoming server settings pane, one of your SMTP server settings pane, and the complete error message, other suggestions may be forthcoming. Thank you.