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Network Working Group                                          T. HansenRequest for Comments: 3887                             AT&T LaboratoriesCategory: Standards Track                                 September 2004Message Tracking Query ProtocolStatus of this Memo   This document specifies an Internet standards track protocol for the   Internet community, and requests discussion and suggestions for   improvements.  Please refer to the current edition of the "Internet   Official Protocol Standards" (STD 1) for the standardization state   and status of this protocol.  Distribution of this memo is unlimited.Copyright Notice   Copyright (C) The Internet Society (2004).Abstract   Customers buying enterprise message systems often ask: Can I track   the messages?  Message tracking is the ability to find out the path   that a particular message has taken through a messaging system and   the current routing status of that message.  This document describes   the Message Tracking Query Protocol that is used in conjunction with   extensions to the ESMTP protocol to provide a complete message   tracking solution for the Internet.1.  Introduction   The Message Tracking Models and Requirements document   [RFC-MTRK-MODEL] discusses the models that message tracking solutions   could follow, along with requirements for a message tracking solution   that can be used with the Internet-wide message infrastructure.  This   memo and its companions, [RFC-MTRK-ESMTP] and [RFC-MTRK-TSN],   describe a complete message tracking solution that satisfies those   requirements.  The memo [RFC-MTRK-ESMTP] defines an extension to the   SMTP service that provides the information necessary to track   messages.  This memo defines a protocol that can be used to query the   status of messages that have been transmitted on the Internet via   SMTP.  The memo [RFC-MTRK-TSN] describes the message/tracking-status   [RFC-MIME] media type that is used to report tracking status   information.  Using the model document's terminology, this solution   uses active enabling and active requests with both request and   chaining referrals.Hansen                      Standards Track                     [Page 1]

RFC 3887            Message Tracking Query Protocol       September 20041.1.  Terminology   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",   "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this   document are to be interpreted as described inBCP 14,RFC 2119   [RFC-KEYWORDS].   All syntax descriptions use the ABNF specified by [RFC-ABNF].   Terminal nodes not defined elsewhere in this document are defined in   [RFC-ABNF], [RFC-URI], [RFC-MTRK-ESMTP], [RFC-SMTP], or   [RFC-SMTPEXT].2.  Basic Operation   The Message Tracking Query Protocol (MTQP) is similar to many other   line-oriented Internet protocols, such as [POP3] and [NNTP].   Initially, the server host starts the MTQP service by listening on   TCP port 1038.   When an MTQP client wishes to make use of the message tracking   service, it establishes a TCP connection with the server host, as   recorded from the initial message submission or as returned by a   previous tracking request.  To find the server host, the MTQP client   first does an SRV lookup for the server host using DNS SRV records,   with a service name of "mtqp" and a protocol name of "tcp", as in   _mtqp._tcp.smtp3.example.com.  (See the "Usage rules" section in   [RFC-SRV] for details.)  If the SRV records do not exist, the MTQP   client then does an address record lookup for the server host.  When   the connection is established, the MTQP server sends a greeting.  The   MTQP client and MTQP server then exchange commands and responses   (respectively) until the connection is closed or aborted.2.1.  Tracking Service DNS Considerations   Because of the ways server host lookups are performed, many different   tracking server host configurations are supported.   A mail system that uses a single mail server host and has the MTQP   server host on the same server host will most likely have a single MX   record pointing at the server host, and if not, will have an address   record.  Both mail and MTQP clients will access that host directly.   A mail system that uses a single mail server host, but wants tracking   queries to be performed on a different machine, MUST have an SRV MTQP   record pointing at that different machine.Hansen                      Standards Track                     [Page 2]

RFC 3887            Message Tracking Query Protocol       September 2004   A mail system that uses multihomed mail servers has two choices for   providing tracking services: either all mail servers must be running   tracking servers that are able to retrieve information on all   messages, or the tracking service must be performed on one (or more)   machine(s) that are able to retrieve information on all messages.  In   the former case, no additional DNS records are needed beyond the MX   records already in place for the mail system.  In the latter case,   SRV MTQP records are needed that point at the machine(s) that are   running the tracking service.  In both cases, note that the tracking   service MUST be able to handle the queries for all messages accepted   by that mail system.2.2.  Commands   Commands in MTQP consist of a case-insensitive keyword, possibly   followed by one or more parameters.  All commands are terminated by a   CRLF pair.  Keywords and parameters consist of printable ASCII   characters.  Keywords and parameters are separated by whitespace (one   or more space or tab characters).  A command line is limited to 998   characters before the CRLF.2.3.  Responses   Responses in MTQP consist of a status indicator that indicates   success or failure.  Successful commands may also be followed by   additional lines of data.  All response lines are terminated by a   CRLF pair and are limited to 998 characters before the CRLF.  There   are several status indicators: "+OK" indicates success; "+OK+"   indicates a success followed by additional lines of data, a multi-   line success response; "-TEMP" indicates a temporary failure; "-ERR"   indicates a permanent failure; and "-BAD" indicates a protocol error   (such as for unrecognized commands).   A status indicator MAY be followed by a series of machine-parsable,   case-insensitive response information giving more data about the   errors.  These are separated from the status indicator and each other   by a single slash character ("/", decimal code 47).  Following that,   there MAY be white space and a human-readable text message.  The   human-readable text message is not intended to be presented to the   end user, but should be appropriate for putting in a log for use in   debugging problems.   In a multi-line success response, each subsequent line is terminated   by a CRLF pair and limited to 998 characters before the CRLF.  When   all lines of the response have been sent, a final line is sent   consisting of a single period (".", decimal code 046) and a CRLF   pair.  If any line of the multi-line response begins with a period,   the line is "dot-stuffed" by prepending the period with a secondHansen                      Standards Track                     [Page 3]

RFC 3887            Message Tracking Query Protocol       September 2004   period.  When examining a multi-line response, the client checks to   see if the line begins with a period.  If so, and octets other than   CRLF follow, the first octet of the line (the period) is stripped   away.  If so, and if CRLF immediately follows the period, then the   response from the MTQP server is ended and the line containing the   ".CRLF" is not considered part of the multi-line response.   An MTQP server MUST respond to an unrecognized, unimplemented, or   syntactically invalid command by responding with a negative -BAD   status indicator.  A server MUST respond to a command issued when the   session is in an incorrect state by responding with a negative -ERR   status indicator.2.4.  Firewall Considerations   A firewall mail gateway has two choices when receiving a tracking   query for a host within its domain: it may return a response to the   query that says the message has been passed on, but no further   information is available; or it may perform a chaining operation   itself, gathering information on the message from the mail hosts   behind the firewall, and returning to the MTQP client the information   for each behind-the-firewall hop, or possibly just the final hop   information, possibly also disguising the names of any hosts behind   the firewall.  Which option is picked is an administrative decision   and is not further mandated by this document.   If a server chooses to perform a chaining operation itself, it MUST   provide a response within 2 minutes, and SHOULD return a "no further   information is available" response if it cannot provide an answer at   the end of that time limit.2.5.  Optional Timers   An MTQP server MAY have an inactivity autologout timer.  Such a timer   MUST be of at least 10 minutes in duration.  The receipt of any   command from the client during that interval should suffice to reset   the autologout timer.  An MTQP server MAY limit the number of   commands, unrecognized commands, or total connection time, or MAY use   other criteria, to prevent denial of service attacks.   An MTQP client MAY have an inactivity autologout timer while waiting   for a response from the server.  Since an MTQP server may be a   firewall, and may be chaining information from other servers, such a   timer MUST be at least 2 minutes in duration.Hansen                      Standards Track                     [Page 4]

RFC 3887            Message Tracking Query Protocol       September 20043.  Initialization and Option Response   Once the TCP connection has been opened by an MTQP client, the MTQP   server issues an initial status response that indicates its   readiness.  If the status response is positive (+OK or +OK+), the   client may proceed with other commands.   The initial status response MUST include the response information   "/MTQP".  Negative responses MUST include a reason code as response   information.  The following reason codes are defined here;   unrecognized reason codes added in the future may be treated as   equivalent to "unavailable".      "/" "unavailable"      "/" "admin"   The reason code "/admin" SHOULD be used when the service is   unavailable for administrative reasons.  The reason code   "/unavailable" SHOULD be used when the service is unavailable for   other reasons.   If the server has any options enabled, they are listed as the multi-   line response of the initial status response, one per line.  An   option specification consists of an identifier, optionally followed   by option-specific parameters.  An option specification may be   continued onto additional lines by starting the continuation lines   with white space.  The option identifier is case insensitive.  Option   identifiers beginning with the characters "vnd." are reserved for   vendor use.  (See below.)   One option specification is defined here:   STARTTLS [1*WSP "required"]   This capability MUST be listed if the optional STARTTLS command is   enabled on the MQTP server and one or more certificates have been   properly installed.   It has one optional parameter: the word "required" (The parameters   for STARTTLS are case-insensitive).  If the server requires that TLS   be used for some of the domains the server handles, the server MUST   specify the "required" parameter.Hansen                      Standards Track                     [Page 5]

RFC 3887            Message Tracking Query Protocol       September 20043.1.  Examples   Example #1 (no options):   S: +OK/MTQP MTQP server ready   Example #2 (service temporarily unavailable):   S: -TEMP/MTQP/admin Service down for admin, call back later   Example #3 (service permanently unavailable):   S: -ERR/MTQP/unavailable Service down   Example #4 (alternative for no options):   S: +OK+/MTQP MTQP server ready   S: .   Example #5 (options available):   S: +OK+/MTQP MTQP server ready   S: starttls   S: vnd.com.example.option2 with parameters private to example.com   S: vnd.com.example.option3 with a very long   S:  list of parameters   S: .4.  TRACK Command   Syntax:   track-command = "TRACK" 1*WSP unique-envid 1*WSP mtrk-secret CRLF     mtrk-secret = base64   Unique-envid is defined in [RFC-MTRK-ESMTP].  Mtrk-secret is the   secret A described in [RFC-MTRK-ESMTP], encoded using base64.   When the client issues the TRACK command, and the user is validated,   the MTQP server retrieves tracking information about an email   message.  To validate the user, the value of mtrk-secret is hashed   using SHA1, as described in [RFC-SHA1].  The hash value is then   compared with the value passed with the message when it was   originally sent.  If the hash values match, the user is validated.   A successful response MUST be multi-line, consisting of a [RFC-MIME]   body part.  The MIME body part MUST be of type multipart/related,   with subparts of message/tracking-status, as defined in   [RFC-MTRK-TSN].  The response contains the tracking information about   the email message that used the given tracking-id.  A negative   response to the TRACK command may include these reason codes:Hansen                      Standards Track                     [Page 6]

RFC 3887            Message Tracking Query Protocol       September 2004      "/" "tls-required"      "/" "admin"      "/" "unavailable"      "/" "noinfo"      "/" "insecure"   The reason code "/tls-required" SHOULD be used when the server has   decided to require TLS.  The reason code "/admin" SHOULD be used when   the server has become unavailable, due to administrative reasons,   since the connection was initialized.  The reason code "/unavailable"   SHOULD be used when the server has become unavailable, for other   reasons, since the connection was initialized.  The reason code   "/insecure" is described later.   If a message has not been seen by the MTQP server, the server MUST   choose between two choices: it MAY return a positive response with an   action field of "opaque" in the tracking information, or it MAY   return a negative response with a reason code of "noinfo".4.1.  Examples   In each of the examples below, the unique-envid is   "<12345-20010101@example.com>", the secret A is "abcdefgh", and the   SHA1 hash B is (in hex) "734ba8b31975d0dbae4d6e249f4e8da270796c94".   The message came from example.com and the MTQP server is   example2.com.Example #6      Message Delivered:C: TRACK <12345-20010101@example.com> YWJjZGVmZ2gKS: +OK+ Tracking information followsS: Content-Type: multipart/related; boundary=%%%%; type=tracking-statusS:S: --%%%%S: Content-Type: message/tracking-statusS:S: Original-Envelope-Id: 12345-20010101@example.comS: Reporting-MTA: dns; example2.comS: Arrival-Date: Mon, 1 Jan 2001 15:15:15 -0500S:S: Original-Recipient:rfc822; user1@example1.comS: Final-Recipient:rfc822; user1@example1.comS: Action: deliveredS: Status: 2.5.0S:S: --%%%%--S: .Hansen                      Standards Track                     [Page 7]

RFC 3887            Message Tracking Query Protocol       September 2004Example #7      Message Transferred:C: TRACK <12345-20010101@example.com> YWJjZGVmZ2gKS: +OK+ Tracking information followsS: Content-Type: multipart/related; boundary=%%%%; type=tracking-statusS:S: --%%%%S: Content-Type: message/tracking-statusS:S: Original-Envelope-Id: 12345-20010101@example.comS: Reporting-MTA: dns; example2.comS: Arrival-Date: Mon,  1 Jan 2001 15:15:15 -0500S:S: Original-Recipient:rfc822; user1@example1.comS: Final-Recipient:rfc822; user1@example1.comS: Action: transferredS: Remote-MTA: dns; example3.comS: Last-Attempt-Date: Mon, 1 Jan 2001 19:15:03 -0500S: Status:2.4.0S:S: --%%%%--S: .Example #8 Message Delayed and a Dot-Stuffed Header:C: TRACK <12345-20010101@example.com> YWJjZGVmZ2gKS: +OK+ Tracking information followsS: Content-Type: multipart/related; boundary=%%%%; type=tracking-statusS: ..Dot-Stuffed-Header: as an exampleS:S: --%%%%S: Content-Type: message/tracking-statusS:S: Original-Envelope-Id: 12345-20010101@example.comS: Reporting-MTA: dns; example2.comS: Arrival-Date: Mon, 1 Jan 2001 15:15:15 -0500S:S: Original-Recipient:rfc822; user1@example1.comS: Final-Recipient:rfc822; user1@example1.comS: Action: delayedS: Status: 4.4.1 (No answer from host)S: Remote-MTA: dns; example3.comS: Last-Attempt-Date: Mon, 1 Jan 2001 19:15:03 -0500S: Will-Retry-Until: Thu, 4 Jan 2001 15:15:15 -0500S:S: --%%%%--S: .Hansen                      Standards Track                     [Page 8]

RFC 3887            Message Tracking Query Protocol       September 2004Example #9 Two Users, One Relayed, One Failed:C: TRACK <12345-20010101@example.com> YWJjZGVmZ2gKS: +OK+ Tracking information followsS: Content-Type: multipart/related; boundary=%%%%; type=tracking-statusS:S: --%%%%S: Content-Type: message/tracking-statusS:S: Original-Envelope-Id: 12345-20010101@example.comS: Reporting-MTA: dns; example2.comS: Arrival-Date: Mon,  1 Jan 2001 15:15:15 -0500S:S: Original-Recipient:rfc822; user1@example1.comS: Final-Recipient:rfc822; user1@example1.comS: Action: relayedS: Status: 2.1.9S: Remote-MTA: dns; example3.comS: Last-Attempt-Date: Mon, 1 Jan 2001 19:15:03 -0500S:S: Original-Recipient:rfc822; user2@example1.comS: Final-Recipient:rfc822; user2@example1.comS: Action: failedS: Status 5.2.2 (Mailbox full)S: Remote-MTA: dns; example3.comS: Last-Attempt-Date: Mon, 1 Jan 2001 19:15:03 -0500S:S: --%%%%--S: .Example #10 Firewall:C: TRACK <12345-20010101@example.com> YWJjZGVmZ2gKS: +OK+ Tracking information followsS: Content-Type: multipart/related; boundary=%%%%; type=tracking-statusS:S: --%%%%S: Content-Type: message/tracking-statusS:S: Original-Envelope-Id: 12345-20010101@example.comS: Reporting-MTA: dns; example2.comS: Arrival-Date: Mon,  1 Jan 2001 15:15:15 -0500S:S: Original-Recipient:rfc822; user1@example1.comS: Final-Recipient:rfc822; user1@example1.comS: Action: relayedS: Status: 2.1.9S: Remote-MTA: dns; smtp.example3.comS: Last-Attempt-Date: Mon, 1 Jan 2001 19:15:03 -0500S:Hansen                      Standards Track                     [Page 9]

RFC 3887            Message Tracking Query Protocol       September 2004S: --%%%%S: Content-Type: message/tracking-statusS:S: Original-Envelope-Id: 12345-20010101@example.comS: Reporting-MTA: dns; smtp.example3.comS: Arrival-Date: Mon,  1 Jan 2001 15:15:15 -0500S:S: Original-Recipient:rfc822; user2@example1.comS: Final-Recipient:rfc822; user4@example3.comS: Action: deliveredS: Status: 2.5.0S:S: --%%%%--S: .Example #11 Firewall, Combining Per-Recipient Blocks:C: TRACK <12345-20010101@example.com> YWJjZGVmZ2gKS: +OK+ Tracking information followsS: Content-Type: multipart/related; boundary=%%%%; type=tracking-statusS:S: --%%%%S: Content-Type: message/tracking-statusS:S: Original-Envelope-Id: 12345-20010101@example.comS: Reporting-MTA: dns; example2.comS: Arrival-Date: Mon,  1 Jan 2001 15:15:15 -0500S:S: Original-Recipient:rfc822; user1@example1.comS: Final-Recipient:rfc822; user1@example1.comS: Action: relayedS: Status: 2.1.9S: Remote-MTA: dns; smtp.example3.comS: Last-Attempt-Date: Mon, 1 Jan 2001 19:15:03 -0500S:S: Original-Recipient:rfc822; user2@example1.comS: Final-Recipient:rfc822; user4@example3.comS: Action: deliveredS: Status:2.5.0S:S: --%%%%--S: .Hansen                      Standards Track                    [Page 10]

RFC 3887            Message Tracking Query Protocol       September 2004Example #12 Firewall, Hiding System Names Behind the Firewall:C: TRACK <12345-20010101@example.com> YWJjZGVmZ2gKS: +OK+ Tracking information followsS: Content-Type: multipart/related; boundary=%%%%; type=tracking-statusS:S: --%%%%S: Content-Type: message/tracking-statusS:S: Original-Envelope-Id: 12345-20010101@example.comS: Reporting-MTA: dns; example2.comS: Arrival-Date: Mon,  1 Jan 2001 15:15:15 -0500S:S: Original-Recipient:rfc822; user1@example1.comS: Final-Recipient:rfc822; user1@example1.comS: Action: relayedS: Status: 2.1.9S: Remote-MTA: dns; example2.comS: Last-Attempt-Date: Mon, 1 Jan 2001 19:15:03 -0500S:S: --%%%%S: Content-Type: message/tracking-statusS:S: Original-Envelope-Id: 12345-20010101@example.comS: Reporting-MTA: dns; example2.comS: Arrival-Date: Mon,  1 Jan 2001 15:15:15 -0500S:S: Original-Recipient:rfc822; user2@example1.comS: Final-Recipient:rfc822; user4@example1.comS: Action: deliveredS: Status: 2.5.0S:S: --%%%%--S: .5.  COMMENT Command   Syntax:     comment-command =  "COMMENT" opt-text CRLF            opt-text = [WSP *(VCHAR / WSP)]   When the client issues the COMMENT command, the MTQP server MUST   respond with a successful response (+OK or +OK+).  All optional text   provided with the COMMENT command are ignored.Hansen                      Standards Track                    [Page 11]

RFC 3887            Message Tracking Query Protocol       September 20046.  STARTTLS Command   Syntax:     starttls-command = "STARTTLS" 1*WSP domain *WSP CRLF               domain = (sub-domain 1*("." sub-domain))   TLS [TLS] is a popular mechanism for enhancing TCP communications   with confidentiality and authentication.  All MTQP servers MUST   implement TLS.  However, TLS MAY be disabled by a server   administrator, either explicitly or by failing to install any   certificates for TLS to use.  If an MTQP server supports TLS and has   one or more certificates available it MUST include "STARTTLS" in the   option specifications list on protocol startup.      Note: TLS SHOULD be enabled on MQTP servers whenever possible.   The parameter MUST be a fully qualified domain name (FQDN).  A client   MUST specify the hostname it believes it is speaking with so that the   server may respond with the proper TLS certificate.  This is useful   for virtual servers that provide message tracking for multiple   domains (i.e., virtual hosting).   If the server returns a negative response, it MAY use one of the   following response codes:      "/" "unsupported"      "/" "unavailable"      "/" "tls-in-progress"      "/" "bad-fqdn"   If TLS is not supported, then a response code of "/unsupported"   SHOULD be used.  If TLS is not available for some other reason, then   a response code of "/unavailable" SHOULD be used.  If a TLS session   is already in progress, then it is a protocol error and "-BAD" MUST   be returned with a response code of "/tls-in-progress".  If there is   a mismatch between the supplied FQDN and the FQDN found in the   dNSName field of the subjectAltName extension of the server's   certificate [RFC-X509], then it is a protocol error and "-BAD" MUST   be returned with a response code of "/bad-fqdn".   After receiving a positive response to a STARTTLS command, the client   MUST start the TLS negotiation before giving any other MTQP commands.   If the MTQP client is using pipelining (see below), the STARTTLS   command must be the last command in a group.Hansen                      Standards Track                    [Page 12]

RFC 3887            Message Tracking Query Protocol       September 20046.1.  Processing After the STARTTLS Command   If the TLS handshake fails, the server SHOULD abort the connection.   After the TLS handshake has been completed, both parties MUST   immediately decide whether or not to continue based on the   authentication and confidentiality achieved.  The MTQP client and   server may decide to move ahead even if the TLS negotiation ended   with no authentication and/or no confidentiality because most MTQP   services are performed with no authentication and no confidentiality,   but some MTQP clients or servers may want to continue only if a   particular level of authentication and/or confidentiality was   achieved.   If the MTQP client decides that the level of authentication or   confidentiality is not high enough for it to continue, it SHOULD   issue an MTQP QUIT command immediately after the TLS negotiation is   complete.   If the MTQP server decides that the level of authentication or   confidentiality is not high enough for it to continue, it MAY abort   the connection.  If it decides that the level of authentication or   confidentiality is not high enough for it to continue, and it does   not abort the connection, it SHOULD reply to every MTQP command from   the client (other than a QUIT command) with a negative "-ERR"   response and a response code of "/insecure".6.2.  Result of the STARTTLS Command   Upon completion of the TLS handshake, the MTQP protocol is reset to   the initial state (the state in MTQP after a server starts up).  The   server MUST discard any knowledge obtained from the client prior to   the TLS negotiation itself.  The client MUST discard any knowledge   obtained from the server, such as the list of MTQP options, which was   not obtained from the TLS negotiation itself.   At the end of the TLS handshake, the server acts as if the connection   had been initiated and responds with an initial status response and,   optionally, a list of server options.  The list of MTQP server   options received after the TLS handshake MUST be different than the   list returned before the TLS handshake.  In particular, a server MUST   NOT return the STARTTLS option in the list of server options after a   TLS handshake has been completed.   Both the client and the server MUST know if there is a TLS session   active.  A client MUST NOT attempt to start a TLS session if a TLS   session is already active.Hansen                      Standards Track                    [Page 13]

RFC 3887            Message Tracking Query Protocol       September 20047.  QUIT Command      Syntax:        quit-command = "QUIT" CRLF   When the client issues the QUIT command, the MTQP session terminates.   The QUIT command has no parameters.  The server MUST respond with a   successful response.  The client MAY close the session from its end   immediately after issuing this command (if the client is on an   operating system where this does not cause problems).8.  Pipelining   The MTQP client may elect to transmit groups of MTQP commands in   batches without waiting for a response to each individual command.   The MTQP server MUST process the commands in the order received.   Specific commands may place further constraints on pipelining.  For   example, STARTTLS must be the last command in a batch of MTQP   commands.8.1.  Examples   The following two examples are identical:   Example #13 :   C: TRACK <tracking-id> YWJjZGVmZ2gK   S: +OK+ Tracking information follows   S:   S: ... tracking details #1      go here ...   S: .   C: TRACK <tracking-id-2> QUJDREVGR0gK   S: +OK+ Tracking information follows   S:   S: ... tracking details #2      go here ...   S: .Hansen                      Standards Track                    [Page 14]

RFC 3887            Message Tracking Query Protocol       September 2004   Example #14 :   C: TRACK <tracking-id> YWJjZGVmZ2gK   C: TRACK <tracking-id-2> QUJDREVGR0gK   S: +OK+ Tracking information follows   S:   S: ... tracking details #1      go here ...   S: .   S: +OK+ Tracking information follows   S:   S: ... tracking details #2      go here ...   S: .9.  The MTQP URI Scheme9.1.  Intended usage   The MTQP URI scheme is used to designate MTQP servers on Internet   hosts accessible using the MTQP protocol.  It performs an MTQP query   and returns tracking status information.9.2.  URI Scheme Name   The name of the URI scheme is "mtqp".9.3.  URI Scheme Syntax   An MTQP URI takes one of the following forms:      mtqp://<mserver>/track/<unique-envid>/<mtrk-secret>      mtqp://<mserver>:<port>/track/<unique-envid>/<mtrk-secret>   The first form is used to refer to an MTQP server on the standard   port, while the second form specifies a non-standard port.  Both of   these forms specify that the TRACK command is to be issued using the   given tracking id (unique-envid) and authorization secret (mtrk-   secret).  The path element "/track/" MUST BE treated case   insensitively, but the unique-envid and mtrk-secret MUST NOT be.9.3.1.  Formal Syntax   This is an ABNF description of the MTQP URI.   mtqp-uri = "mtqp://" authority "/track/" unique-envid "/" mtrk-secretHansen                      Standards Track                    [Page 15]

RFC 3887            Message Tracking Query Protocol       September 20049.4.  Encoding Rules   The encoding of unique-envid is discussed in [RFC-MTRK-ESMTP].   Mtrk-secret is required to be base64 encoded.  If the "/", "?" and   "%" octets appear in unique-envid or mtrk-secret, they are further   required to be represented by a "%" followed by two hexadecimal   characters.  (The two characters give the hexadecimal representation   of that octet).10.  IANA Considerations   System port number 1038 has been assigned to the Message Tracking   Query Protocol by the Internet Assigned Numbers Authority (IANA).   The service name "MTQP" has been registered with the IANA.   The IANA has also registered the URI registration template found inAppendix A in accordance with [BCP35].   This document requests that IANA maintain one new registry: MTQP   options.  The registry's purpose is to register options to this   protocol.  Options whose names do not begin with "vnd." MUST be   defined in a standards track or IESG approved experimental RFC.  New   MTQP options MUST include the following information as part of their   definition:      option identifier      option parameters      added commands      standard commands affected      specification reference      discussion   One MTQP option is defined in this document, with the following   registration definition:      option identifier: STARTTLS      option parameters: none      added commands: STARTTLS      standard commands affected: none      specification reference:RFC 3887      discussion: seeRFC 3887   Additional vendor-specific options for this protocol have names that   begin with "vnd.".  After the "vnd." would appear the reversed domain   name of the vendor, another dot ".", and a name for the option   itself.  For example, "vnd.com.example.extinfo" might represent aHansen                      Standards Track                    [Page 16]

RFC 3887            Message Tracking Query Protocol       September 2004   vendor-specific extension providing extended information by the owner   of the "example.com" domain.  These names MAY be registered with   IANA.11.  Security Considerations   If the originator of a message were to delegate his or her tracking   request to a third party, this would be vulnerable to snooping over   unencrypted sessions.  The user can decide on a message-by-message   basis if this risk is acceptable.   The security of tracking information is dependent on the randomness   of the secret chosen for each message and the level of exposure of   that secret.  If different secrets are used for each message, then   the maximum exposure from tracking any message will be that single   message for the time that the tracking information is kept on any   MTQP server.  If this level of exposure is too much, TLS may be used   to reduce the exposure further.   It should be noted that message tracking is not an end-to-end   mechanism.  Thus, if an MTQP client/server pair decide to use TLS   confidentiality, they are not securing tracking queries with any   prior or successive MTQP servers.   Both the MTQP client and server must check the result of the TLS   negotiation to see whether acceptable authentication or   confidentiality was achieved.  Ignoring this step completely   invalidates using TLS for security.  The decision about whether   acceptable authentication or confidentiality was achieved is made   locally, is implementation-dependent, and is beyond the scope of this   document.   The MTQP client and server should note carefully the result of the   TLS negotiation.  If the negotiation results in no confidentiality,   or if it results in confidentiality using algorithms or key lengths   that are deemed not strong enough, or if the authentication is not   good enough for either party, the client may choose to end the MTQP   session with an immediate QUIT command, or the server may choose to   not accept any more MTQP commands.   A man-in-the-middle attack can be launched by deleting the "STARTTLS"   option response from the server.  This would cause the client not to   try to start a TLS session.  An MTQP client can protect against this   attack by recording the fact that a particular MTQP server offers TLS   during one session and generating an alarm if it does not appear in   an option response for a later session.Hansen                      Standards Track                    [Page 17]

RFC 3887            Message Tracking Query Protocol       September 2004   Similarly, the identity of the server as expressed in the server's   certificate should be cached, and an alarm generated if they do not   match in a later session.   If TLS is not used, a tracking request is vulnerable to replay   attacks, such that a snoop can later replay the same handshake again   to potentially gain more information about a message's status.   Before the TLS handshake has begun, any protocol interactions are   performed in the clear and may be modified by an active attacker.   For this reason, clients and servers MUST discard any knowledge   obtained prior to the start of the TLS handshake upon completion of   the TLS handshake.   If a client/server pair successfully performs a TLS handshake and the   server does chaining referrals, then the server SHOULD attempt to   negotiate TLS at the same (or better) security level at the next hop.   In a hop-by-hop scenario, STARTTLS is a request for "best effort"   security and should be treated as such.   SASL is not used because authentication is per message rather than   per user.12.  Protocol Syntax   This is a collected ABNF description of the MTQP protocol.mtqp-uri = "mtqp://" authority "/track/" unique-envid "/" mtrk-secretconversation = command-response *(client-command command-response); client sideclient-command = track-command / starttls-command / quit-command/comment-commandtrack-command = "TRACK" 1*WSP unique-envid 1*WSP mtrk-secret CRLFmtrk-secret = base64starttls-command = "STARTTLS" 1*WSP domain *WSP CRLFdomain = (sub-domain 1*("." sub-domain))quit-command = "QUIT" CRLFcomment-command = "COMMENT" opt-text CRLFHansen                      Standards Track                    [Page 18]

RFC 3887            Message Tracking Query Protocol       September 2004; server sidecommand-response = success-response / temp-response / error-response /bad-responsetemp-response = "-TEMP" response-info opt-text CRLFopt-text = [WSP *(VCHAR / WSP)]error-response = "-ERR" response-info opt-text CRLFbad-response = "-BAD" response-info opt-text CRLFsuccess-response = single-line-success / multi-line-successsingle-line-success = "+OK" response-info opt-text CRLFmulti-line-success = "+OK+" response-info opt-text CRLF                               *dataline dotcrlfdataline = *998OCTET CRLFdotcrlf = "." CRLFNAMECHAR = ALPHA / DIGIT / "-" / "_"response-info = *(      "/" ( "admin" / "unavailable" / "unsupported"/ "tls-in-progress" / "insecure" / "tls-required" / 1*NAMECHAR ) )13.  Acknowledgements   The description of STARTTLS is based on [RFC-SMTP-TLS].Hansen                      Standards Track                    [Page 19]

RFC 3887            Message Tracking Query Protocol       September 200414.  References14.1.  Normative References   [RFC-MIME]         Freed, N. and N. Borenstein, "Multipurpose                      Internet Mail Extensions (MIME) Part One: Format                      of Internet Message Bodies",RFC 2045, November                      1996.   [RFC-ABNF]         Crocker, D., Ed. and P. Overell, "Augmented BNF                      for Syntax Specifications: ABNF",RFC 2234,                      November 1997.   [RFC-SRV]          Gulbrandsen, A., Vixie, P., and L. Esibov, "A DNS                      RR for specifying the location of services (DNS                      SRV)",RFC 2782, February 2000.   [RFC-SMTP]         Klensin, J., "Simple Mail Transfer Protocol",RFC2821, April 2001.   [RFC-SMTPEXT]      Myers, J., "SMTP Service Extension for                      Authentication",RFC 2554, March 1999.   [RFC-MTRK-ESMTP]   Allman, E. and T. Hansen, "SMTP Service Extension                      for Message Tracking",RFC 3885, September 2004.   [RFC-MTRK-MODEL]   Hansen, T., "Message Tracking Models and                      Requirements",RFC 3885, September 2004.   [RFC-MTRK-TSN]     Allman, E., "The Message/Tracking-Status MIME                      Extension",RFC 3886, September 2004.   [RFC-URI]          Berners-Lee, T., Fielding, R. and L. Masinter,                      "Uniform Resource Identifiers (URI): Generic                      Syntax",RFC 2396, August 1998.   [TLS]              Dierks, T. and C. Allen, "The TLS Protocol Version                      1.0",RFC 2246, January 1999.Hansen                      Standards Track                    [Page 20]

RFC 3887            Message Tracking Query Protocol       September 200414.2.  Informational References   [BCP35]            Petke, R. and I. King, "Registration Procedures                      for URL Scheme Names",BCP 35,RFC 2717, November                      1999.   [RFC-SHA1]         Eastlake, D. and P. Jones, "US Secure Hash                      Algorithm 1 (SHA1)",RFC 3174, September 2001.   [RFC-KEYWORDS]     Bradner, S., "Key words for use in RFCs to                      Indicate Requirement Levels",BCP 14,RFC 2119,                      March 1997.   [RFC-SMTP-TLS]     Hoffman, P., "SMTP Service Extension for Secure                      SMTP over Transport Layer Security",RFC 3207,                      February 2002.   [RFC-X509]         Housley, R., Polk, W., Ford, W. and D. Solo,                      "Internet X.509 Public Key Infrastructure                      Certificate and Certificate Revocation List (CRL)                      Profile",RFC 3280, April 2002.   [POP3]             Myers, J. and M. Rose, "Post Office Protocol -                      Version 3", STD 53,RFC 1939, May 1996.   [NNTP]             Kantor, B. and P. Lapsley, "Network News Transfer                      Protocol",RFC 977, February 1986.Hansen                      Standards Track                    [Page 21]

RFC 3887            Message Tracking Query Protocol       September 2004Appendix A. MTQP URI Registration Template   Scheme name: mtqp   Scheme syntax: seesection 9.1   Character encoding considerations: seesection 9.4   Intended usage: seesection 9.3   Applications and/or protocols which use this scheme: MTQP   Interoperability considerations: as specified for MTQP   Security considerations: seesection 11.0   Relevant publications: [RFC-MTRK-ESMTP], [RFC-MTRK-MODEL],   [RFC-MTRK-TSN]   Contact: MSGTRK Working Group   Author/Change Controller: IESGAuthor's Address   Tony Hansen   AT&T Laboratories   Middletown, NJ 07748   USA   Phone: +1.732.420.8934   EMail: tony+msgtrk@maillennium.att.comHansen                      Standards Track                    [Page 22]

RFC 3887            Message Tracking Query Protocol       September 2004Full Copyright Statement   Copyright (C) The Internet Society (2004).   This document is subject to the rights, licenses and restrictions   contained inBCP 78, and except as set forth therein, the authors   retain all their rights.   This document and the information contained herein are provided on an   "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/S HE   REPRESENTS OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY AND THE   INTERNET ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS OR   IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF   THE INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED   WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.Intellectual Property   The IETF takes no position regarding the validity or scope of any   Intellectual Property Rights or other rights that might be claimed to   pertain to the implementation or use of the technology described in   this document or the extent to which any license under such rights   might or might not be available; nor does it represent that it has   made any independent effort to identify any such rights.  Information   on the IETF's procedures with respect to rights in IETF Documents can   be found inBCP 78 andBCP 79.   Copies of IPR disclosures made to the IETF Secretariat and any   assurances of licenses to be made available, or the result of an   attempt made to obtain a general license or permission for the use of   such proprietary rights by implementers or users of this   specification can be obtained from the IETF on-line IPR repository athttp://www.ietf.org/ipr.   The IETF invites any interested party to bring to its attention any   copyrights, patents or patent applications, or other proprietary   rights that may cover technology that may be required to implement   this standard.  Please address the information to the IETF at ietf-   ipr@ietf.org.Acknowledgement   Funding for the RFC Editor function is currently provided by the   Internet Society.Hansen                      Standards Track                    [Page 23]