Thunderbird has been my email client for 7 years. This message showed up recently:
Sending of password did not succeed. Mail server inbound.att.net responded: Incorrect username or password. (#MBR1212)
This has worked before:
Go to "Preference" (Tools/Options/Advanced) - select the "General" tab, and look for "Config Editor" - well you know your can muck it all up, so OK the warning, it is highly in place. In the search box, type "Login" and up comes 5 lines for password prompt. Click on "False" and set this "true".
It didn't work this time though.
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