My Dell XPS 420 desktop recently crashed.  I attempted to set up an account in Windows Mail for my email.  It imported my recent emails, but none of my older emails.  I had important messages saved that I need to retrieve.  My email account is through att.net.  I had another computer crash prior to this one and I was able to import everything into that email account.  I don't know what happened with this one. 

I appreciate any help you can provide.