What have you done since last night.. You obviously implemented your email somewhere.. Directory or somethng?
The older your yahoo email address gets...the more spam it will begin to have. I have had the same email for about 7 years and everytime I check it I have 1000+ junk mails sitting in it. People scan yahoo member directories, game rooms, chat rooms, etc. to get your id and add it to a list. Then they just spam the hell out of everyone.