Lost Mail when removed pop account to re-add as imap account
You're going to have a hard time recovering the files and should power off the machine / only mount that drive in read-only mode until you have given up on the idea of data recovery.

I like Data Rescue 3 - but your tool will probably be mostly equivalent.

Look to recover ~/Library/Mail and ~/Library/Mail Downloads files if possible. Ideally you can get the computer friendly - human hostile directory structure back and recover all files with these extensions intact:


emlx
plist