487 lines
16 KiB
Scheme
487 lines
16 KiB
Scheme
;;; SMTP client code -*- Scheme -*-
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;;; This file is part of the Scheme Untergrund Networking package.
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;;; Copyright (c) 1995 by Brian D. Carlstrom and Olin Shivers.
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;;; Copyright (c) 2002-2003 by Mike Sperber <sperber@informatik.uni-tuebingen.de>
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;;; For copyright information, see the file COPYING which comes with
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;;; the distribution.
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;;; See rfc821: http://www.ietf.org/rfc/rfc0821.txt
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;;; SMTP protocol procedures tend to return two values:
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;;; - CODE The integer SMTP reply code returned by server for the transaction.
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;;; - TEXT A list of strings -- the text messages tagged by the code.
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;;; The text strings have the initial code numerals and the terminating
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;;; cr/lf's stripped. Codes in the range [1,399] are sucess codes; codes
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;;; in the range [400,599] are error codes; codes >= 600 are not part
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;;; of the official SMTP spec. This module uses codes >= 600 to indicate
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;;; extra-protocol errors. There are two of these:
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;;; - 600 Server reply could not be parsed.
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;;; The server sent back some sort of incomprehensible garbage reply.
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;;; - 621 Premature EOF while reading server reply.
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;;; The server shut down in the middle of a reply.
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;;; A list of the official protocol return codes is appended at the end of
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;;; this file.
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;;; These little cover functions are trivial packagings of the protocol.
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;;; You could write your own to handle, e.g., mailing a message to a list
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;;; of addresses.
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;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
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(define (smtp-send-mail from to-list headers body . maybe-host)
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(call-with-current-continuation
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(lambda (bailout)
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(let* ((host (:optional maybe-host "localhost"))
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(local (if (string=? host "localhost")
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(system-name) ; we don't need any DNS for that
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(system-fqdn)))
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(connection (smtp-connect host)))
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(receive (code text)
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(smtp-transactions/no-close connection ; Do prologue.
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(smtp-helo local)
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(smtp-mail from))
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(if (>= code 400)
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(values code text) ; error
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;; Send over recipients and collect the losers.
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(let ((losers (filter-map
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(lambda (to)
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(receive (code text)
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((smtp-rcpt to) (smtp-connection-socket connection))
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(and (>= code 400) ; Error
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(cond ((>= code 600)
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(smtp-quit
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(smtp-connection-socket connection))
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(bailout code text))
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(else `(,to ,code ,@text))))))
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to-list)))
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;; Send the message body and wrap things up.
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(receive (code text)
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(smtp-transactions connection
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(smtp-data (normalize-headers headers) body))
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(if (and (< code 400) (null? losers))
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(values code text)
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(values 700 losers))))))))))
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(define (normalize-headers headers)
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(if (assq 'date headers)
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headers
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(cons (cons 'date
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(rfc822-time->string (time)))
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headers)))
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(define (smtp-query socket query arg)
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(receive (code text)
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(smtp-transactions socket
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(smtp-helo (system-name))
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(query arg))
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(values code text)))
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(define (smtp-expand name host)
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(smtp-query (smtp-connect host) smtp-expn name))
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(define (smtp-verify name host)
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(smtp-query (smtp-connect host) smtp-vrfy name))
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(define (smtp-get-help host . details)
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(smtp-query (smtp-connect host) smtp-help (apply string-append (cons " " details))))
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(define (smtp-transactions connection . transactions)
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(let ((socket (smtp-connection-socket connection)))
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(receive (code text) (apply smtp-transactions/no-close connection transactions)
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(cond
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((or (= code 221)
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(= code 421))
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(values))
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(else
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(smtp-quit socket)))
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(values code text))))
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(define (smtp-transactions/no-close connection . transactions)
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(let loop ((transactions transactions))
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(receive (code text) ((car transactions) (smtp-connection-socket connection))
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(if (or (null? (cdr transactions))
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(= code 221)
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(= code 421) ; Redundant, I know.
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(<= 400 code))
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(values code text)
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(loop (cdr transactions))))))
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;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
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;;; The basics of the protocol
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(define (nullary-smtp-command command)
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(lambda (socket)
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(let ((port (socket:outport socket)))
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(write-string command port)
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(write-crlf port))
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(handle-smtp-reply socket)))
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(define (unary-smtp-command command)
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(lambda (data)
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(lambda (socket)
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(let ((port (socket:outport socket)))
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(write-string command port)
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(display #\space port)
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(write-string data port)
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(write-crlf port))
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(handle-smtp-reply socket))))
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(define-record-type smtp-connection :smtp-connection
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(make-smtp-connection socket)
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smtp-connection?
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(socket smtp-connection-socket))
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(define (smtp-connect host . maybe-port)
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(let ((sock (socket-connect protocol-family/internet socket-type/stream host
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(:optional maybe-port "smtp"))))
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(receive (code text) (handle-smtp-reply sock)
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(if (< code 400)
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(make-smtp-connection sock)
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(error "SMTP socket-open server-reply error" sock code text)))))
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;; HELLO <local-hostname>
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(define smtp-helo (unary-smtp-command "HELO"))
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;; MAIL FROM: <sender-address>
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(define smtp-mail (unary-smtp-command "MAIL FROM:"))
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;; RECIPIENT TO: <destination-address>
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(define smtp-rcpt (unary-smtp-command "RCPT TO:"))
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;; DATA
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(define smtp-data
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(let ((send-DATA-msg (nullary-smtp-command "DATA")))
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(lambda (headers message) ; MESSAGE is a list of strings or an input port.
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(lambda (socket)
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(receive (code text) (send-DATA-msg socket)
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(if (>= code 400)
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(values code text) ; Error.
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;; We got a positive acknowledgement for the DATA msg,
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;; now send the message body.
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(let ((p (socket:outport socket)))
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(for-each (lambda (pair)
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(display (symbol->field-name (car pair)) p)
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(write-char #\: p)
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(display (cdr pair) p)
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(write-crlf p))
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headers)
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(write-crlf p)
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(cond ((or (null? message) (pair? message))
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(for-each (lambda (line)
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(write-data-line line p))
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message))
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((input-port? message)
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(let lp ()
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(let ((stuff (read-line message)))
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(if (not (eof-object? stuff))
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(begin
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(write-data-line stuff p)
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(newline))))))
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(else (error "Message must be string or input-port.")))
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(write-crlf p)
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(write-char #\. p)
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(write-crlf p)
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(force-output p)
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(handle-smtp-reply socket))))))))
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(define component-charset (char-set-complement (char-set #\-)))
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(define (symbol->field-name symbol)
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(let ((components (string-tokenize (symbol->string symbol) component-charset)))
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(string-join (map upcase-string components) "-")))
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(define (upcase-string strng)
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(if (string=? "" strng)
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""
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(string-append (string (char-upcase (string-ref strng 0)))
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(substring strng 1 (string-length strng)))))
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(define (write-data-line line port)
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(display (if (string=? line ".")
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".."
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line)
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port)
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(write-crlf port))
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;; SEND FROM: <sender-address>
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(define smtp-send (unary-smtp-command "SEND FROM:"))
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;; SEND OR MAIL <sender-address>
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(define smtp-soml (unary-smtp-command "SOML FROM:"))
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;; SEND AND MAIL <sender-address>
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(define smtp-saml (unary-smtp-command "SOML SAML:"))
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;; RESET
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(define smtp-rset (nullary-smtp-command "RSET"))
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;; VERIFY <user>
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(define smtp-vrfy (unary-smtp-command "VRFY"))
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;; EXPAND <user>
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(define smtp-expn (unary-smtp-command "EXPN"))
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;; HELP <details>
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(define smtp-help
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(let ((send-help (unary-smtp-command "HELP")))
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(lambda details
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(send-help (apply string-append details)))))
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;; NOOP
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(define smtp-noop (nullary-smtp-command "NOOP"))
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;; QUIT
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(define smtp-quit
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(let ((quit (nullary-smtp-command "QUIT")))
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(lambda (socket)
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(receive (code text) (quit socket) ; Quit & close socket gracefully.
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(case code
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((221 421))
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(else (close-socket socket))) ; But close in any event.
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(values code text)))))
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;; TURN
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(define smtp-turn (nullary-smtp-command "TURN"))
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;;; Read and handle the reply. Return an integer (the reply code),
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;;; and a list of the text lines that came tagged by the reply code.
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;;; The text lines have the reply-code prefix (first 4 chars) and the
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;;; terminating cr/lf's stripped.
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;;;
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;;; In bdc's analog of this proc, he would read another reply if the code was
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;;; in the one-hundred range (1xx). These codes aren't even used in smtp,
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;;; according to the RFC. So why?
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(define (handle-smtp-reply socket)
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(receive (code text) (read-smtp-reply (socket:inport socket))
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(case code
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((221 421) (close-socket socket))) ; All done.
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(values code text)))
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;;; Read a reply from the SMTP server. Returns two values:
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;;; - CODE Integer. The reply code.
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;;; - TEXT String list. A list of the text lines comprising the reply.
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;;; Each line of text is stripped of the initial reply-code
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;;; numerals (e.g., the first four chars of the reply), and
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;;; the trailing cr/lf. We are in fact generous about what
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;;; we take to be a line -- the protocol requires cr/lf
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;;; terminators, but we'll accept just lf. This appears to
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;;; true to the spirit of the "be strict in what you send,
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;;; and generous in what you accept" Internet protocol philosphy.
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(define (read-smtp-reply port)
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(let lp ((replies '()))
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(let ((ln (read-crlf-line port)))
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(if (eof-object? ln)
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(values 621 (cons "Premature EOF during smtp reply."
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(reverse replies)))
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(receive (code line more?) (parse-smtp-reply ln)
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(let ((replies (cons line replies)))
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(if more?
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(lp replies)
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(values code (reverse replies)))))))))
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;;; Parse a line of SMTP reply. Return three values:
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;;; CODE integer - the reply code that prefixes the string.
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;;; REST string - the rest of the line.
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;;; MORE? boolean - is there more reply to read (i.e., was the numeric
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;;; reply code terminated by a "-" character?)
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(define (parse-smtp-reply line)
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(if (and (string? line) ; This is all checking
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(> (string-length line) 3) ; to see if the line
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(char-numeric? (string-ref line 0)) ; is properly formatted.
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(char-numeric? (string-ref line 1))
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(char-numeric? (string-ref line 2))
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(let ((c (string-ref line 3)))
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(or (char=? c #\space) (char=? c #\-))))
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(values (string->number (substring line 0 3)) ; It is.
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(substring line 4 (string-length line))
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(char=? (string-ref line 3) #\-))
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(values 600 ; It isn't.
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(string-append "Improperly-formatted smtp reply: " line)
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#f)))
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;;; Reply codes
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;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
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;;; This material taken from the RFC.
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;;;
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;;; 1yz Positive Preliminary reply
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;;;
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;;; The command has been accepted, but the requested action
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;;; is being held in abeyance, pending confirmation of the
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;;; information in this reply. The sender-SMTP should send
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;;; another command specifying whether to continue or abort
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;;; the action.
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;;;
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;;; [Note: SMTP does not have any commands that allow this
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;;; type of reply, and so does not have the continue or
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;;; abort commands.]
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;;;
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;;; 2yz Positive Completion reply
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;;;
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;;; The requested action has been successfully completed. A
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;;; new request may be initiated.
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;;;
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;;; 3yz Positive Intermediate reply
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;;;
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;;; The command has been accepted, but the requested action
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;;; is being held in abeyance, pending receipt of further
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;;; information. The sender-SMTP should send another command
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;;; specifying this information. This reply is used in
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;;; command sequence groups.
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;;;
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;;; 4yz Transient Negative Completion reply
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;;;
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;;; The command was not accepted and the requested action did
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;;; not occur. However, the error condition is temporary and
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;;; the action may be requested again. The sender should
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;;; return to the beginning of the command sequence (if any).
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;;; It is difficult to assign a meaning to "transient" when
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;;; two different sites (receiver- and sender- SMTPs) must
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;;; agree on the interpretation. Each reply in this category
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;;; might have a different time value, but the sender-SMTP is
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;;; encouraged to try again. A rule of thumb to determine if
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;;; a reply fits into the 4yz or the 5yz category (see below)
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;;; is that replies are 4yz if they can be repeated without
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;;; any change in command form or in properties of the sender
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;;; or receiver. (E.g., the command is repeated identically
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;;; and the receiver does not put up a new implementation.)
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;;;
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;;; 5yz Permanent Negative Completion reply
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;;;
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;;; The command was not accepted and the requested action did
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;;; not occur. The sender-SMTP is discouraged from repeating
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;;; the exact request (in the same sequence). Even some
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;;; "permanent" error conditions can be corrected, so the
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;;; human user may want to direct the sender-SMTP to
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;;; reinitiate the command sequence by direct action at some
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;;; point in the future (e.g., after the spelling has been
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;;; changed, or the user has altered the account status).
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;;;
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;;;The second digit encodes responses in specific categories:
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;;;
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;;; x0z Syntax -- These replies refer to syntax errors,
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;;; syntactically correct commands that don't fit any
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;;; functional category, and unimplemented or superfluous
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;;; commands.
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;;;
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;;; x1z Information -- These are replies to requests for
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;;; information, such as status or help.
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;;;
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;;; x2z Connections -- These are replies referring to the
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;;; transmission channel.
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;;;
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;;; x3z Unspecified as yet.
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;;;
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;;; x4z Unspecified as yet.
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;;;
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;;; x5z Mail system -- These replies indicate the status of
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;;; the receiver mail system vis-a-vis the requested
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;;; transfer or other mail system action.
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;;; Complete list (grouped by function)
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;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
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;;; 500 Syntax error, command unrecognized
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;;; [This may include errors such as command line too long]
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;;; 501 Syntax error in parameters or arguments
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;;; 502 Command not implemented
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;;; 503 Bad sequence of commands
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;;; 504 Command parameter not implemented
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;;;
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;;; 211 System status, or system help reply
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;;; 214 Help message
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;;; [Information on how to use the receiver or the meaning of a
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;;; particular non-standard command; this reply is useful only
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;;; to the human user]
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;;;
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;;; 220 <domain> Service ready
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;;; 221 <domain> Service closing transmission channel
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;;; 421 <domain> Service not available,
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;;; closing transmission channel
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;;; [This may be a reply to any command if the service knows it
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;;; must shut down]
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;;;
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;;; 250 Requested mail action okay, completed
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;;; 251 User not local; will forward to <forward-path>
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;;; 450 Requested mail action not taken: mailbox unavailable
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;;; [E.g., mailbox busy]
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;;; 550 Requested action not taken: mailbox unavailable
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;;; [E.g., mailbox not found, no access]
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;;; 451 Requested action aborted: error in processing
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;;; 551 User not local; please try <forward-path>
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;;; 452 Requested action not taken: insufficient system storage
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;;; 552 Requested mail action aborted: exceeded storage allocation
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;;; 553 Requested action not taken: mailbox name not allowed
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;;; [E.g., mailbox syntax incorrect]
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;;; 354 Start mail input; end with <CRLF>.<CRLF>
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;;; 554 Transaction failed
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;;;
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;;; State diagram
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;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
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;;; CONNECTION ESTABLISHMENT
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;;; S: 220
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;;; F: 421
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;;; HELO
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;;; S: 250
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;;; E: 500, 501, 504, 421
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;;; MAIL
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;;; S: 250
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;;; F: 552, 451, 452
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;;; E: 500, 501, 421
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;;; RCPT
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;;; S: 250, 251
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;;; F: 550, 551, 552, 553, 450, 451, 452
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;;; E: 500, 501, 503, 421
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;;; DATA
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;;; I: 354 -> data -> S: 250
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;;; F: 552, 554, 451, 452
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;;; F: 451, 554
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;;; E: 500, 501, 503, 421
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;;; RSET
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;;; S: 250
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;;; E: 500, 501, 504, 421
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;;; SEND
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;;; S: 250
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;;; F: 552, 451, 452
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;;; E: 500, 501, 502, 421
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;;; SOML
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;;; S: 250
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;;; F: 552, 451, 452
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;;; E: 500, 501, 502, 421
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;;; SAML
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;;; S: 250
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;;; F: 552, 451, 452
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;;; E: 500, 501, 502, 421
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;;; VRFY
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;;; S: 250, 251
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;;; F: 550, 551, 553
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;;; E: 500, 501, 502, 504, 421
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;;; EXPN
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;;; S: 250
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;;; F: 550
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;;; E: 500, 501, 502, 504, 421
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;;; HELP
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;;; S: 211, 214
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;;; E: 500, 501, 502, 504, 421
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;;; NOOP
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;;; S: 250
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;;; E: 500, 421
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;;; QUIT
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;;; S: 221
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;;; E: 500
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;;; TURN
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;;; S: 250
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;;; F: 502
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;;; E: 500, 503
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