Hi Jeff,
I have not tried this so proceed at own risk !
If you only have 3 (or basically very few) users to worry about, how about :-
0) check out and note down the ownership / permissions of the user home folders ( /home/e-smith/files/users/)
1) copy out each users home folders (either directly to the new server or first to an ibay, then to a Windows PC)
2) when the new server is up, recreate all the users
3) copy back the home folders you backed up (including all hidden folders)
4) check and redo the appropriate owner / permissions for the files / folders you copied back.
I think everything to do with a user's mail lives under their home folders so, copying the entire folder out then back and restoring the permissions / ownership *should* work.
Good Luck !
Kelvin