Comment 0 for bug 1241167

https://help.ubuntu.com/community/Kerberos

"Principals
Principals are entries in the Kerberos database that represent users or services on the network. Each user or service that is participates in a Kerberos authentication realm must have a principal defined in the Kerberos database.

User principals take the form <email address hidden>. For instance, user tom on the EXAMPLE.COM realm should have a principal <email address hidden> in the Kerberos database.

Service principals take the form <email address hidden>. For example, the FTP service on lab.example.com in the EXAMPLE.COM realm would have the principal <email address hidden> in the Kerberos database.

Principal names are case sensitive."

This one is a bit chicken and egg.

It would seem windows returns principle names in the form host.DOMAIN@DOMAIN

whilst the ubuntu implementaion is host.domain@Domain

with kerb being case sensitive its brings the question who is right or what is the fix?