How do I recover the emails that disappeared after changing my email address??

When I first set up my email on "Mail" I used a hotmail account. Automatically, all the emails from hotmail.com were saved on my macbook and "deleted" from the website. Now I changed my hotmail account through which I get emails on my macbook and all the emails I had disappeared! I can't find them on the website either because they had previously disappeared from there as well!!! How do I now recover those emails that I had with my previous account????