What is the difference between content-language and accept-language headers in Outlook? How/when are these added?

Question

Outlook 2010 | Windows 7

Can someone please elaborate on the difference between the content-language and accept-language email headers?

When do these get added by Outlook 2010 and where can I configured these values?

Here's an example:

From: Mike <mike@foo.com>
To: Bob <bob@foo2.com>
Date: Tue, 9 Oct 2012 11:25:30 -0700
Subject: Test Message
Thread-Topic: Test Message
Thread-Index: Ac2mSsdlkfjsdlkfjlsdfsd4k04YqkZA==
Message-ID: <B870629719727B4BA82A6C0DLSKJFLSKDJFLSDKJFLSKDFJ2@mailserver.foo.com>
Accept-Language: en-US
Content-Language: en-US
X-MS-Has-Attach: 
X-MS-TNEF-Correlator:

I'm aware that for HTTP, Content-Language is from the server, and lets the client know what language(s) are present on the requested page. Accept-Language is from the client, and lets the server know the user's preferred language(s). Is this the same for email?

I have a use case where I'd like a downstream content-filter to key off the language header and perform an action if a certain language is present.

I'm guessing that these are set in the Outlook Options >> Language section but would like confirmation.