I sold my computer, now someone is reading my emails! How can I stop them?

I forgot to delete my 'MS Outlook Express' email address before I sold my old computer. It seems the person who how has it is looking at my email. How can I stop them and delete me emails off the old computer?

You can not prevent them from reading your already downloaded offline mails, all you can do it change your password from you email provider.

There is no way to stop the buyer of your computer from reading your emails already on that computer, you should have deleted them before you sold it.

Just change your password ASAP!