It could depend on your ISP and the email software that you use. If it is Apple Mail and you have not emptied the Mail Trash, they might still be there. Mail Preferences allows you to set the duration before the Trash is emptied. Similarly, if your mail is coming through someone like Yahoo, Gmail, etc., if you access the mail through a browser, there may be a similar situation as with Mail.
And even if you us Apple Mail exclusively, you can still go to the provider's mail website via a browser and check there, too.
