2.2.3.2.11 Language Properties

To set the value of the PidTagMessageLocaleId property ([MS-OXCMSG] section 2.2.1.5), clients MUST set the Content-Language header, as specified in [RFC3282].

MIME readers set the value of the PidTagMessageLocaleId property by extracting the first language tag from the value of the Content-Language header and mapping it to an LCID, as specified in [MS-LCID]. MIME readers SHOULD use the value of a Content-Language header (2) in preference to the value of the PidTagMessageLocaleId property found in the attMsgProps attribute, as specified in [MS-OXTNEF] section 2.1.3.3.21, of a TNEF message.

To set the value of the PidNameAcceptLanguage property ([MS-OXCMSG] section 2.2.1.42), clients SHOULD write the value to an Accept-Language header. Clients MAY write an X-Accept-Language header instead.

MIME readers SHOULD<114> copy the value of either header to the value of the PidNameAcceptLanguage property. If both headers are present, MIME readers SHOULD use the Accept-Language header.