Losing old e-mail account

Hello,
I tried to change the password of my old e-mail( alimanss579@yahoo.com ) but I was told ( this is a valid password...)
so maney times , and when I got fed up of repeating my attempts , I ended that action and returned back to my old password , but I was shocked when it did not work anymore and now I cannot sign in to this e-mail .I have so maney important messeges and information saved in that e-mail.Please help me help me ... to get it back.
NOTE:
I tried getting it back throughout getting the old password procedures but I remember just one of the security answers and it did not help.I tried to transfer the messeges to my new e-mail and it did not help either.
Best regards
Ali