RFC 937 (rfc937) - Page 2 of 24

Post Office Protocol: Version 2

RFC 937                                                    February 1985
Post Office Protocol


   we expect the user's mail to be addressed to A
   (not A).

   That is, the destination of the mail is the mailbox on the server
   machine.  The POP2 protocol and the workstation are merely a
   mechanism for viewing the messages in the mailbox.

   The user is not tied to any particular workstation for accessing his
   mail.  The workstation does not appear as any part of the mailbox
   address.

   This is a very simple protocol.  This is not a user interface.  We
   expect that there is a program in the workstation that is friendly to
   the user.  This protocol is not "user friendly".  One basic rule of
   this protocol is "if anything goes wrong close the connection".
   Another basic rule is to have few options.

   POP2 does not parse messages in any way.  It does not analyze message
   headers (Date:, From:, To:, Cc:, or Subject:).  POP2 simply transmits
   whole messages from a mailbox server to a client workstation.

The Protocol

   The POP2 protocol is a sequence of commands and replies.  The design
   draws from many previous protocols of the ARPA-Internet community.

      The server must be listening for a connection.  When a connection
      is opened the server sends a greeting message and waits for
      commands.  When commands are received the server acts on them and
      responds with replies.

      The client opens a connection, waits for the greeting, then sends
      the HELO command with the user name and password arguments to
      establish authorization to access mailboxes.  The server returns
      the number of messages in the default mailbox.

      The client may read the default mailbox associated with the user
      name or may select another mailbox by using the FOLD command.  The
      server returns the number of messages in the mailbox selected.

      The client begins a message reading transaction with a READ
      command.  The read command may optionally indicate which message
      number to read, the default is the current message (incremented
      when a message is read and set to one when a new folder is
      selected).  The server returns the number of characters in the
      message.




Butler, et. al.