Simple Mail Transfer Protocol
RFC 788

Document Type RFC - Unknown (November 1981; No errata)
Obsoletes RFC 780
Last updated 2013-03-02
Stream Legacy
Formats plain text pdf html bibtex
Stream Legacy state (None)
Consensus Boilerplate Unknown
RFC Editor Note (None)
IESG IESG state RFC 788 (Unknown)
Telechat date
Responsible AD (None)
Send notices to (None)
RFC788
                                                                        

                                    
                                    
                                    
                                    
                                    
                     SIMPLE MAIL TRANSFER PROTOCOL
                                    
                                    
                                    
                           Jonathan B. Postel

                             November 1981
                                    
                                    
                                    
                     Information Sciences Institute
                   University of Southern California
                           4676 Admiralty Way
                   Marina del Rey, California  90291

                             (213) 822-1511


                                                                        
RFC 788                                                    November 1981
                                           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 ..................................... 10
      3.5.  Opening and Closing ..................................... 12
      3.6.  Relaying ................................................ 13
      3.7.  Domains ................................................. 15

   4.  THE SMTP SPECIFICATIONS ...................................... 16

      4.1.  SMTP Commands ........................................... 16
      4.1.1.  Command Semantics ..................................... 16
      4.1.2.  Command Syntax ........................................ 23
      4.2.  SMTP Replies ............................................ 28
      4.2.1.  Reply Codes by Function Group ......................... 29
      4.2.2.  Reply Codes in Numeric Order .......................... 30
      4.3.  Sequencing of Commands and Replies ...................... 31
      4.4.  State Diagrams .......................................... 33
      4.5.  Details ................................................. 35
      4.5.1.  Minimum Implementation ................................ 35
      4.5.2.  Transparency .......................................... 35
      4.5.3.  Sizes ................................................. 36

   APPENDIX A:  TCP ................................................. 38
   APPENDIX B:  NCP ................................................. 39
   APPENDIX C:  NITS ................................................ 40
   APPENDIX D:  X.25 ................................................ 41
   APPENDIX E:  Theory of Reply Codes ............................... 42
   APPENDIX F:  Scenarios ........................................... 45

   GLOSSARY ......................................................... 58

   REFERENCES ....................................................... 61



Network Working Group                                          J. Postel
Request for Comments: 788                                            ISI
Replaces: RFC 780, 772                                     November 1981

                     SIMPLE MAIL TRANSFER PROTOCOL

1.  INTRODUCTION

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

   SMTP is independent of the particular transmission subsystem and
   requires only a reliable ordered data stream channel.  Appendices A,
   B, C, and D describe the use of SMTP with various transport services.
   A Glossary provides the definitions of terms as used in this
   document.

   An important feature of SMTP is its capability to relay mail across
   transport service environments.  A transport service provides an
   interprocess communication environment (IPCE).  An IPCE may cover one
   network, several networks, or a subset of a network.  It is important
   to realize that transport systems (or IPCEs) are not one-to-one with
   networks.  A process can communicate directly with another process
   through any mutually known IPCE.  Mail is an application or use of
   interprocess communication.  Mail can be communicated between
   processes in different IPCEs by relaying through a process connected
   to two (or more) IPCEs.  More specifically, mail can be relayed
   between hosts on different transport systems by a host on both
   transport systems.

Postel                                                          [Page 1]
Show full document text