I want to edit my subaccounts, but can't find a list of them

I'm having trouble asccessing my email, which is through bellsouth.net. I use Thunderbird and POP3 service and it has woorrked for years.

A while back I got a message that my password wasn't working anymore. So, I tried the usual "Reset Password" routine and was issued a new password consisting of six digits and letters. When I tried to use it, I got a message from Yahoo saying that the password was not acceptable because it didn't have 8 characters. I tried adding characters, but of course, that was not correct because it did not martch what I had been given by ATT. So, I'm going around in circles.

I have tried subaccounts and aliases, nop joy. Right now am looking for a listing of all my subaccounts and passwords. I can't find such a list with Bellsouth, ATT, or Yahoo. And I can't get a human on line to help me.

Ca n anyone here guide me through this maze? I have a lot of emails backing up on the server that i can't access.