Hacked email account

I am frankly hacked off! Yesterday, from the page of Mailer-Daemon failure notices on my laptop I realised that summat was up. It appears that some bright spark has apparently hacked into my (old) Yahoo email account and sent bl***y advertising emails to my entire contacts list. Many failed to be delivered as the addresses were no longer in use, but loads of my friends have been subjected to this blankety-blank spam and I feel very embarrassed. I have now changed the password on the account, deleted all the contacts (so no chance of emailing anybody who doesn't email me first!) What more canI do? These have had nothing to do with forwarding funny emails or jokes as they have included DH's former accountant, his former office email address and others I have not used for years - OK should have deleted them before now- and companies like Boden!!!
[egg on face] emoticon +