ISP email account hacked

Hi guys--

I had my ISP email account hacked the other day and the hacker enabled email forwarding (didn't even know it was an option) to a yahoo! account. I changed my password but there's little else I know that I can do to prevent this from happening again. I spoke with my ISP and it seems that this feature cannot be disabled which is very upsetting. I check every few hours to make sure that the email forwarding is still off and delete the forwarding email address, but everytime I go back to check, the email address is still there. I know that he's not in there because the forwarding is off and I receive my test emails.

Please help me protect myself from this sort of thing in the future and whatever suggestions you have, I look forward to hearing them.

Thanks a lot in advance.