OS X :: Lost Emails From Inbox And Draft Folder

Running mail with 2 email accounts, one old one that I could still receive emails from but not send any; the other is the main email that I use. I deleted the old account then could not send any emails. I spoke to my ISP and have fixed the sending problem, but now I seem to have lost a heap of emails, possibly all the ones that had been sent to the old account but also a long one that my wife had just written that was in drafts as it was unable to send. Essentially we want to recover the emails we received, and the one that was in drafts.