Email is a family of protocols rather than one specification.
| Area | Useful RFCs |
|---|---|
| SMTP | RFC 5321 |
| Message format | RFC 5322 |
| Architecture | RFC 5598 |
| Submission | RFC 6409 |
| MIME | RFC 2045–2049 |
| SPF | RFC 7208 |
| DKIM | RFC 6376 |
| DMARC | RFC 9989 |
| ARC | RFC 8617 |
| MTA-STS | RFC 8461 |
| TLS-RPT | RFC 8460 |
| DANE SMTP | RFC 7672 |
| IMAP | RFC 9051 |
| POP3 | RFC 1939 |
| S/MIME | RFC 8551 |
| OpenPGP | RFC 9580 |
Standards are updated and obsoleted over time. Check the RFC Editor page for an RFC before assuming an older document is still the current normative specification.