i received a letter seemingly from yahoo.com after i wrote them about the incredible amounts of spam i have recieved. the address that sent it is 
management@yahoo.com. it seems perty legit but for more info you are to look at an attachment. DO NOT OPEN IT!!! it is a virus. luckly i scanned it (by accident even).
the subject line was Notify about your e-mail account utilization
so just to give you a heads up.
here are the exact words used:
Dear  user  of Yahoo.com gateway e-mail  server,
Some  of  our clients  complained about the spam (negative  e-mail 
content)
outgoing from your e-mail account. Probably, you  have  been infected 
by
a proxy-relay  trojan server. In order to keep your computer  safe,
follow the instructions.
For  details see the  attach.
Attached file protected with the  password for security reasons. 
Password is 11756.
Cheers,
   The Yahoo.com team                               
http://www.yahoo.com
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so again DO NOT OPEN IT