| Subject | English | Japanese |
| comp., MS | X-header | X ヘッダー (" An e-mail message header that begins with "X-".") |
| comp., MS | X-Header storage option | X ヘッダーの挿入 (The option that adds an X-Header to the Internet header of spam messages. Information contained in this X-Header is specified by administrators in the Administration Center) |
| comp., MS | x-ua-compatible header | x-ua-Compatible ヘッダー (An HTML header in which the HTTP-EQUIV property has a value of x-ua-compatible, which allows content to specify the document compatibility modes supported by the webpage) |