Thunderbird will not accept my log in credentials

Please help me login to Thunderbird. My computer was updated and now it won't accept my credentials

who is your mail provider?

ATT/Yahoo mail provider.

Message: Sending of password for user alphamachine@sbcglobal.net did not succeed. Mail server inbound.att.net responded: [SYS/TEMP] Server error - Please try again later.

Saved password: AJKZrl8ERFUO4EprkK1UM3_a8rF_dZYVywXZFA0ALA57EIItZnmexr6Y Where did this password come from? Does not agree with password used in browser.

Can access email thru Yahoo via Firefox browser.