• [3] 3. MIME Header Fields (MIME 頭欄) → MIME頭欄
• [4] 4. MIME-Version: Field
• [5] 5. Content-Type: Field
• [6] 6. Content-Transfer-Encoding: Field
• [7] 7. Content-ID: Field
• [8] 8. Content-Description: Field
• [9] 9. Additional MIME Header Fields (追加の MIME 頭欄) → MIME頭欄