Sounds like you and your "ex" were sharing an email account.
Recommended free email services:
Hotmail --
www.hotmail.comYahoo --
www.yahoo.com Gmail -- mail.google.com
There is no way to take the information back, but if you are at reasonable speaking levels, you could just ask they he/she forward the emails to your new email address.
Be sure to change any online account information (like an eBay account, or Amazon account you may have also bee sharing) to your email address, better yet, to avoid causing him/her problems, make a new one.