rfc1225_pop3.txt

邮件编码格式说明。

                      which permit the client to parse the messages
                      in the maildrop.

                 Note that messages marked as deleted are not counted in
                 either total.

               Possible Responses:
                   +OK nn mm
               Examples:
                   C:    STAT
                   S:    +OK 2 320

           LIST [msg]
               Arguments: a message-id (optionally)  If a message-id is
                   given, it may NOT refer to a message marked as
                   deleted.
               Restrictions: may only be given in the TRANSACTION state.
               Discussion:

                 If an argument was given and the POP3 server issues a
                 positive response with a line containing information
                 for that message.  This line is called a "scan listing"
                 for that message.

                 If no argument was given and the POP3 server issues a
                 positive response, then the response given is
                 multi-line.  After the initial +OK, for each message
                 in the maildrop, the POP3 server responds with a line
                 containing information for that message.  This line
                 is called a "scan listing" for that message.

                 In order to simplify parsing, all POP3 servers are
                 required to use a certain format for scan listings.
                 The first octets present must be the message-id of



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RFC 1225                          POP3                          May 1991


                 the message.  Following the message-id is the size of
                 the message in octets.  This memo makes no requirement
                 on what follows the message size in the scan listing.
                 Minimal implementations should just end that line of
                 the response with a CRLF pair.  More advanced
                 implementations may include other information, as
                 parsed from the message.

                      NOTE: This memo STRONGLY discourages
                      implementations from supplying additional
                      information in the scan listing.  Other, optional,
                      facilities are discussed later on which permit
                      the client to parse the messages in the maildrop.

                 Note that messages marked as deleted are not listed.

               Possible Responses:
                   +OK scan listing follows
                   -ERR no such message
               Examples:
                   C:    LIST
                   S:    +OK 2 messages (320 octets)
                   S:    1 120
                   S:    2 200
                   S:    .
                     ...
                   C:    LIST 2
                   S:    +OK 2 200
                     ...
                   C:    LIST 3
                   S:    -ERR no such message, only 2 messages in
                         maildrop

           RETR msg
               Arguments: a message-id (required)  This message-id may
                   NOT refer to a message marked as deleted.
               Restrictions: may only be given in the TRANSACTION state.
               Discussion:

                 If the POP3 server issues a positive response, then the
                 response given is multi-line.  After the initial +OK,
                 the POP3 server sends the message corresponding to the
                 given message-id, being careful to byte-stuff the
                 termination character (as with all multi-line
                 responses).

                 If the number associated with this message is higher
                 than the "highest number accessed" in the maildrop, the



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RFC 1225                          POP3                          May 1991


                 POP3 server updates the "highest number accessed" to
                 the number associated with this message.

               Possible Responses:
                   +OK message follows
                   -ERR no such message
               Examples:
                   C:    RETR 1
                   S:    +OK 120 octets
                   S:    <the POP3 server sends the entire message here>
                   S:    .

           DELE msg
               Arguments: a message-id (required)  This message-id
                   may NOT refer to a message marked as deleted.
               Restrictions: may only be given in the TRANSACTION state.
               Discussion:

                 The POP3 server marks the message as deleted.  Any
                 future reference to the message-id associated with the
                 message in a POP3 command generates an error.  The POP3
                 server does not actually delete the message until the
                 POP3 session enters the UPDATE state.

                 If the number associated with this message is higher
                 than the "highest number accessed" in the maildrop,
                 the POP3 server updates the "highest number accessed"
                 to the number associated with this message.

               Possible Responses:
                   +OK message deleted
                   -ERR no such message
               Examples:
                   C:    DELE 1
                   S:    +OK message 1 deleted
                     ...
                   C:    DELE 2
                   S:    -ERR message 2 already deleted

           NOOP
               Arguments: none
               Restrictions: may only be given in the TRANSACTION state.
               Discussion:

                 The POP3 server does nothing, it merely replies with a
                 positive response.

               Possible Responses:



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RFC 1225                          POP3                          May 1991


                   +OK
               Examples:
                   C:    NOOP
                   S:    +OK

           LAST
               Arguments: none
               Restrictions: may only be issued in the TRANSACTION state.
               Discussion:

                 The POP3 server issues a positive response with a line
                 containing the highest message number which accessed.
                 Zero is returned in case no message in the maildrop has
                 been accessed during previous transactions.  A client
                 may thereafter infer that messages, if any, numbered
                 greater than the response to the LAST command are
                 messages not yet accessed by the client.

             Possible Response:
                   +OK nn

             Examples:
                   C:      STAT
                   S:      +OK 4 320
                   C:      LAST
                   S:      +OK 1
                   C:      RETR 3
                   S:      +OK 120 octets
                   S:      <the POP3 server sends the entire message
                           here>
                   S:      .
                   C:      LAST
                   S:      +OK 3
                   C:      DELE 2
                   S:      +OK message 2 deleted
                   C:      LAST
                   S:      +OK 3
                   C:      RSET
                   S:      +OK
                   C:      LAST
                   S:      +OK 1

           RSET
               Arguments: none
               Restrictions: may only be given in the TRANSACTION
                   state.
               Discussion:




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RFC 1225                          POP3                          May 1991


                 If any messages have been marked as deleted by the POP3
                 server, they are unmarked.  The POP3 server then
                 replies with a positive response.  In addition, the
                 "highest number accessed" is also reset to the value
                 determined at the beginning of the POP3 session.

               Possible Responses:
                   +OK
               Examples:
                   C:    RSET
                   S:    +OK maildrop has 2 messages (320 octets)



The UPDATE State

   When the client issues the QUIT command from the TRANSACTION state,
   the POP3 session enters the UPDATE state.  (Note that if the client
   issues the QUIT command from the AUTHORIZATION state, the POP3
   session terminates but does NOT enter the UPDATE state.)

           QUIT
               Arguments: none
               Restrictions: none
               Discussion:

                 The POP3 server removes all messages marked as deleted
                 from the maildrop.  It then releases the
                 exclusive-access lock on the maildrop and replies as
                 to the success of
                 these operations.  The TCP connection is then closed.

               Possible Responses:
                   +OK
               Examples:
                   C:    QUIT
                   S:    +OK dewey POP3 server signing off (maildrop
                         empty)
                     ...
                   C:    QUIT
                   S:    +OK dewey POP3 server signing off (2 messages
                         left)
                     ...


Optional POP3 Commands

   The POP3 commands discussed above must be supported by all minimal



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RFC 1225                          POP3                          May 1991


   implementations of POP3 servers.

   The optional POP3 commands described below permit a POP3 client
   greater freedom in message handling, while preserving a simple POP3
   server implementation.

                 NOTE: This memo STRONGLY encourages implementations to
                 support these commands in lieu of developing augmented
                 drop and scan listings.  In short, the philosophy of
                 this memo is to put intelligence in the part of the
                 POP3 client and not the POP3 server.

           TOP msg n
               Arguments: a message-id (required) and a number.  This
                   message-id may NOT refer to a message marked as
                   deleted.
               Restrictions: may only be given in the TRANSACTION state.
               Discussion:

                 If the POP3 server issues a positive response, then
                 the response given is multi-line.  After the initial
                 +OK, the POP3 server sends the headers of the message,
                 the blank line separating the headers from the body,
                 and then the number of lines indicated message's body,
                 being careful to byte-stuff the termination character
                 (as with all multi-line responses).

                 Note that if the number of lines requested by the POP3
                 client is greater than than the number of lines in the
                 body, then the POP3 server sends the entire message.

               Possible Responses:
                   +OK top of message follows
                   -ERR no such message