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Simple Mail Transfer Protocol (RFC0821)

IP.com Disclosure Number: IPCOM000003869D
Original Publication Date: 1982-Aug-01
Included in the Prior Art Database: 2000-Sep-13

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J. Postel: AUTHOR

Abstract

The objective of Simple Mail Transfer Protocol (SMTP) is to transfer mail reliably and efficiently.

This text was extracted from a ASCII Text document.
This is the abbreviated version, containing approximately 3% of the total text.

RFC 821

SIMPLE MAIL TRANSFER PROTOCOL

Jonathan B. Postel

August 1982

Information Sciences Institute

University of Southern California

4676 Admiralty Way

Marina del Rey, California 90291

(213) 822-1511

RFC 821 August 1982

Simple Mail Transfer Protocol

TABLE OF CONTENTS

1. INTRODUCTION .................................................. 1

2. THE SMTP MODEL ................................................ 2

3. THE SMTP PROCEDURE ............................................ 4

3.1. Mail ..................................................... 4

3.2. Forwarding ............................................... 7

3.3. Verifying and Expanding .................................. 8

3.4. Sending and Mailing ..................................... 11

3.5. Opening and Closing ..................................... 13

3.6. Relaying ................................................ 14

3.7. Domains ................................................. 17

3.8. Changing Roles .......................................... 18

4. THE SMTP SPECIFICATIONS ...................................... 19

4.1. SMTP Commands ........................................... 19

4.1.1. Command Semantics ..................................... 19

4.1.2. Command Syntax ........................................ 27

4.2. SMTP Replies ............................................ 34

4.2.1. Reply Codes by Function Group ......................... 35

4.2.2. Reply Codes in Numeric Order .......................... 36

4.3. Sequencing of Commands and Replies ...................... 37

4.4. State Diagrams .......................................... 39

4.5. Details ................................................. 41

4.5.1. Minimum Implementation ................................ 41

4.5.2. Transparency .......................................... 41

4.5.3. Sizes ................................................. 42

APPENDIX A: TCP ................................................. 44

APPENDIX B: NCP ................................................. 45

APPENDIX C: NITS ................................................ 46

APPENDIX D: X.25 ................................................ 47

APPENDIX E: Theory of Reply Codes ............................... 48

APPENDIX F: Scenarios ........................................... 51

GLOSSARY ......................................................... 64

REFERENCES ....................................................... 67

Network Working Group J. Postel

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