Which mail header does Outlook 2003+ use to indicate the confidentiality?

When you compose a message in Outlook 2003 and choose 'Confidential' from the Options->Sensitivity box, which mail header is used to indicate that setting? Do/will newer versions of Outlook use the same header as Outlook 2003 does? Is this process standardized?

Sensitivity: company-confidential

Or:

Sensitivity: personal
Sensitivity: private

I checked this on Outlook 2007, I don't think there's any reason that it would have changed in 2010 (to maintain compatibility to emails sent between versions).

As to whether it's "standardized", it probably falls into the same category as most of Microsoft's cute custom headers: They're standards in Microsoft's imagination and under their roof only.

Regarding the question, whether this is standardaized. Actually, this time Microsoft followed RFC 2156 (Mapping between X.400 and RFC 822/MIME). Have a look here for the definition of the sensitivity mail header. Additionally, the IETF lists this header in the current version of "Registration of Mail and MIME Header Fields" (RFC 4021)