hacked email address

my boss email address wat hacked into by someone whose very cunning,i dont know how to go ahead wit it so any help wil be helpful

email dormain is hotmail,the guy has changed the password and my boss forgot the security question so am stuck.apparently my boss filled something asking about his email add and password as authentication since then the add was taken over and the guy sent mails to people on his address book saying hes stuck in london they send him money