| RFC | Название | статус | примечание | |
| 1521 | MIME (Multipurpose Internet Mail Extensions) Part One: Mechanisms for Specifying and Describing the Format of Internet Message Bodies | DRAFT STANDARD | Obsoletes 1341. Obsoleted by 2045, 2046, 2047, 2048, 2049. Updated by 1590 | |
| 1522 | MIME (Multipurpose Internet Mail Extensions) Part Two: Message Header Extensions for Non-ASCII Text | DRAFT STANDARD | Obsoletes 1342. Obsoleted by 2045, 2046, 2047, 2048, 2049 | |
| 1870 | SMTP Service Extension for Message Size Declaration | STANDARD | Obsoletes 1653 |
| 2045 | Multipurpose Internet Mail Extensions (MIME) Part One: Format of Internet Message Bodies | DRAFT STANDARD | Obsoletes 1521, 1522, 1590, Updated by 2184, 2231 | |
| 2046 | Multipurpose Internet Mail Extensions (MIME) Part Two: Media Types | DRAFT STANDARD | Obsoletes 1521, 1522, 1590. Updated by 2646, 3798 | |
| 2047 | MIME (Multipurpose Internet Mail Extensions) Part Three: Message Header Extensions for Non-ASCII Text. | DRAFT STANDARD | Заголовки типа =?koi8-r?Q?=D4=C5=D3=D4?=. Obsoletes 1521, 1522, 1590. Updated by 2184, 2231 | |
| 2554 | SMTP Service Extension for Authentication | PROPOSED STANDARD | | |
| 2683 | IMAP4 Implementation Recommendations | INFORMATIONAL | | |
| 2920 | SMTP Service Extension for Command Pipelining | STD | Obsoletes 2197 |
| 3461 | Simple Mail Transfer Protocol (SMTP) Service Extension for Delivery Status Notifications (DSNs) | DRAFT STANDAR | Obsoletes 1891. Updated by 3798, 3885 | |
| 3462 | The Multipart/Report Content Type for the Reporting of Mail System Administrative Messages | DRAFT STANDAR | Obsoletes 1892 | |
| 3463 | Enhanced Mail System Status Codes | DRAFT STANDAR | Obsoletes 1893. Updated by 3886, 4468 | |
| 3464 | An Extensible Message Format for Delivery Status Notifications | DRAFT STANDAR | Obsoletes 1894 | |
| 3798 | Message Disposition Notification 1) | DRAFT STANDARD | Уведомление о прочтении. Obsoletes 2298, Updates 3461, 2046 | |
| 5321 | Simple Mail Transfer Protocol | DRAFT STANDARD | Obsoletes 2821, Updates 1123 | |