If it were me and I only had a small number of users to deal with, here's what I'd do:
1. Manually create the new users on the 6.0.1 box.
2. Tar the home dirs for all the users on your 5.6 box. For example: tar -cf greg.tar /home/e-smith/files/users/greg (my home dir)
3. Copy the user home dir tar files to the 6.0.1 box via FTP, SMB, etc.
4. Delete the home dirs for all users on the 6.0.1 box.
5. Move the 5.6 user home dir tar files to /home/e-smith/files/users on the 6.0.1 machine and untar them. For example: tar -xf greg.tar
6. Chown all user home dirs to the correct owner. Using greg as the example user there, issue the following: chown -R greg:greg /home/e-smith/files/users/greg
This procedure will preserve your users data and email w/o having to monkey with any of the SME & linux account files.
Greg