path: root/doc/rfc/rfc4409.txt

Network Working Group                                         R. Gellens
Request for Comments: 4409                                      QUALCOMM
Obsoletes: 2476                                               J. Klensin
Category: Standards Track                                     April 2006


                       Message Submission for Mail

Status 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 (2006).

Abstract

   This memo splits message submission from message relay, allowing each
   service to operate according to its own rules (for security, policy,
   etc.), and specifies what actions are to be taken by a submission
   server.

   Message relay and final delivery are unaffected, and continue to use
   SMTP over port 25.

   When conforming to this document, message submission uses the
   protocol specified here, normally over port 587.

   This separation of function offers a number of benefits, including
   the ability to apply specific security or policy requirements.
















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Table of Contents

   1. Introduction ....................................................3
   2. Document Information ............................................4
      2.1. Definitions of Terms Used in This Memo .....................4
      2.2. Conventions Used in This Document ..........................5
   3. Message Submission ..............................................5
      3.1. Submission Identification ..................................5
      3.2. Message Rejection and Bouncing .............................5
      3.3. Authorized Submission ......................................6
   4. Mandatory Actions ...............................................7
      4.1. General Submission Rejection Code ..........................7
      4.2. Ensure All Domains Are Fully-Qualified .....................7
      4.3. Require Authentication .....................................8
   5. Recommended Actions .............................................8
      5.1. Enforce Address Syntax .....................................8
      5.2. Log Errors .................................................8
   6. Optional Actions ................................................9
      6.1. Enforce Submission Rights ..................................9
      6.2. Enforce Permissions ........................................9
      6.3. Check Message Data .........................................9
      6.4. Support for the Postmaster Address .........................9
   7. Interaction with SMTP Extensions ...............................10
   8. Message Modifications ..........................................11
      8.1. Add 'Sender' ..............................................11
      8.2. Add 'Date' ................................................11
      8.3. Add 'Message-ID' ..........................................11
      8.4. Transfer Encode ...........................................11
      8.5. Sign the Message ..........................................11
      8.6. Encrypt the Message .......................................12
      8.7. Resolve Aliases ...........................................12
      8.8. Header Rewriting ..........................................12
   9. Security Considerations ........................................12
   10. IANA Considerations ...........................................13
   11. Acknowledgements ..............................................13
   12. Normative References ..........................................14
   13. Informative References ........................................14














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1.  Introduction

   SMTP was defined as a message *transfer* protocol, that is, a means
   to route (if needed) and deliver finished (complete) messages.

   Message Transfer Agents (MTAs) are not supposed to alter the message
   text, except to add 'Received', 'Return-Path', and other header
   fields as required by [SMTP-MTA].

   However, SMTP is now also widely used as a message *submission*
   protocol, that is, a means for Message User Agents (MUAs) to
   introduce new messages into the MTA routing network.  The process
   that accepts message submissions from MUAs is termed a Message
   Submission Agent (MSA).

   In order to permit unconstrained communications, SMTP is not often
   authenticated during message relay.

   Authentication and authorization of initial submissions have become
   increasingly important, driven by changes in security requirements
   and rising expectations that submission servers take responsibility
   for the message traffic they originate.

   For example, due to the prevalence of machines that have worms,
   viruses, or other malicious software that generate large amounts of
   spam, many sites now prohibit outbound traffic on the standard SMTP
   port (port 25), funneling all mail submissions through submission
   servers.

   In addition to authentication and authorization issues, messages
   being submitted are in some cases finished (complete) messages, and
   in other cases are unfinished (incomplete) in one or more aspects.
   Unfinished messages may need to be completed to ensure they conform
   to [MESSAGE-FORMAT], and later requirements.  For example, the
   message may lack a proper 'Date' header field, and domains might not
   be fully qualified.  In some cases, the MUA may be unable to generate
   finished messages (e.g., it might not know its time zone).  Even when
   submitted messages are complete, local site policy may dictate that
   the message text be examined or modified in some way, e.g., to
   conceal local name or address spaces.  Such completions or
   modifications have been shown to cause harm when performed by
   downstream MTAs -- that is, MTAs after the first-hop submission MTA
   -- and are in general considered to be outside the province of
   standardized MTA functionality.

   Separating messages into submissions and transfers allows developers
   and network administrators to more easily do the following:




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   *   Implement security policies and guard against unauthorized mail
       relaying or injection of unsolicited bulk mail

   *   Implement authenticated submission, including off-site submission
       by authorized users such as travelers

   *   Separate the relevant software code differences, thereby making
       each code base more straightforward and allowing for different
       programs for relay and submission

   *   Detect configuration problems with a site's mail clients

   *   Provide a basis for adding enhanced submission services in the
       future

   This memo describes a low-cost, deterministic means for messages to
   be identified as submissions, and specifies what actions are to be
   taken by a submission server.

2.  Document Information

2.1.  Definitions of Terms Used in This Memo

   Many of the concepts and terms used in this document are defined in
   [SMTP-MTA]; familiarity with those documents is assumed here.

   Fully-Qualified

   Containing or consisting of a domain that can be globally resolved
   using the Domain Name Service; that is, not a local alias or partial
   specification.

   Message Submission Agent (MSA)

   A process that conforms to this specification.  An MSA acts as a
   submission server to accept messages from MUAs, and either delivers
   them or acts as an SMTP client to relay them to an MTA.

   Message Transfer Agent (MTA)

   A process that conforms to [SMTP-MTA].  An MTA acts as an SMTP server
   to accept messages from an MSA or another MTA, and either delivers
   them or acts as an SMTP client to relay them to another MTA.








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   Message User Agent (MUA)

   A process that acts (often on behalf of a user and with a user
   interface) to compose and submit new messages, and process delivered
   messages.

   For delivered messages, the receiving MUA may obtain and process the
   message according to local conventions or, in what is commonly
   referred to as a split-MUA model, Post Office Protocol [POP3] or IMAP
   [IMAP4] is used to access delivered messages, whereas the protocol
   defined here (or SMTP) is used to submit messages.

2.2.  Conventions Used in This Document

   In examples, "C:" is used to indicate lines sent by the client, and
   "S:" indicates those sent by the server.  Line breaks within a
   command example are for editorial purposes only.

   Examples use the 'example.net' domain.

   The key words "MUST", "MUST NOT", "SHOULD", "SHOULD NOT", and "MAY"
   in this document are to be interpreted as defined in [KEYWORDS].

3.  Message Submission

3.1.  Submission Identification

   Port 587 is reserved for email message submission as specified in
   this document.  Messages received on this port are defined to be
   submissions.  The protocol used is ESMTP [SMTP-MTA, ESMTP], with
   additional restrictions or allowances as specified here.

   Although most email clients and servers can be configured to use port
   587 instead of 25, there are cases where this is not possible or
   convenient.  A site MAY choose to use port 25 for message submission,
   by designating some hosts to be MSAs and others to be MTAs.

3.2.  Message Rejection and Bouncing

   MTAs and MSAs MAY implement message rejection rules that rely in part
   on whether the message is a submission or a relay.

   For example, some sites might configure their MTAs to reject all RCPT
   commands for messages that do not reference local users, and
   configure their MSA to reject all message submissions that do not
   come from authorized users, with authorization based either on
   authenticated identity or the submitting endpoint being within a
   protected IP environment.



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   NOTE:  It is better to reject a message than to risk sending one that
   is damaged.  This is especially true for problems that are
   correctable by the MUA, for example, an invalid 'From' field.

   If an MSA is not able to determine a return path to the submitting
   user, from a valid MAIL FROM, a valid source IP address, or based on
   authenticated identity, then the MSA SHOULD immediately reject the
   message.  A message can be immediately rejected by returning a 550
   code to the MAIL command.

   Note that a null return path, that is, MAIL FROM:<>, is permitted and
   MUST NOT in itself be cause for rejecting a message.  (MUAs need to
   generate null return-path messages for a variety of reasons,
   including disposition notifications.)

   Except in the case where the MSA is unable to determine a valid
   return path for the message being submitted, text in this
   specification that instructs an MSA to issue a rejection code MAY be
   complied with by accepting the message and subsequently generating a
   bounce message.  (That is, if the MSA is going to reject a message
   for any reason except being unable to determine a return path, it can
   optionally do an immediate rejection or accept the message and then
   mail a bounce.)

   NOTE:  In the normal case of message submission, immediately
   rejecting the message is preferred, as it gives the user and MUA
   direct feedback.  To properly handle delayed bounces, the client MUA
   needs to maintain a queue of messages it has submitted, and match
   bounces to them.  Note that many contemporary MUAs do not have this
   capability.

3.3.  Authorized Submission

   Numerous methods have been used to ensure that only authorized users
   are able to submit messages.  These methods include authenticated
   SMTP, IP address restrictions, secure IP and other tunnels, and prior
   POP authentication.

   Authenticated SMTP [SMTP-AUTH] has seen widespread deployment.  It
   allows the MSA to determine an authorization identity for the message
   submission, one that is not tied to other protocols.

   IP address restrictions are very widely implemented, but do not allow
   for travelers and similar situations, and can be easily spoofed
   unless all transport paths between the MUA and MSA are trustworthy.






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   Secure IP [IPSEC], and other encrypted and authenticated tunneling
   techniques, can also be used and provide additional benefits of
   protection against eavesdropping and traffic analysis.

   Requiring a POP [POP3] authentication (from the same IP address)
   within some amount of time (e.g., 20 minutes) prior to the start of a
   message submission session has also been used, but this does impose
   restrictions on clients as well as servers, which may cause
   difficulties.  Specifically, the client must do a POP authentication
   before an SMTP submission session, and not all clients are capable
   and configured for this.  Also, the MSA must coordinate with the POP
   server, which may be difficult.  There is also a window during which
   an unauthorized user can submit messages and appear to be a
   previously authorized user.  Since it is dependent on the MUA's IP
   addresses, this technique is substantially as subject to IP address
   spoofing as validation based on known IP addresses alone (see above).

4.  Mandatory Actions

   An MSA MUST do all of the following:

4.1.  General Submission Rejection Code

   Unless covered by a more precise response code, response code 554 is
   to be used to reject a MAIL, RCPT, or DATA command that contains
   something improper.

4.2.  Ensure All Domains Are Fully-Qualified

   The MSA MUST ensure that all domains in the SMTP envelope are fully-
   qualified.

   If the MSA examines or alters the message text in any way, except to
   add trace header fields [SMTP-MTA], it MUST ensure that all domains
   in address header fields are fully-qualified.

   Reply code 554 is to be used to reject a MAIL, RCPT, or DATA command
   that contains improper domain references.

   A frequent local convention is to accept single-level domains (e.g.,
   'sales') and then to expand the reference by adding the remaining
   portion of the domain name (e.g., to 'sales.example.net').  Local
   conventions that permit single-level domains SHOULD reject, rather
   than expand, incomplete multi-level domains (e.g., 'squeaky.sales'),
   since such expansion is particularly risky.






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4.3.  Require Authentication

   The MSA MUST by default issue an error response to the MAIL command
   if the session has not been authenticated using [SMTP-AUTH], unless
   it has already independently established authentication or
   authorization (such as being within a protected subnetwork).

   Section 3.3 discusses authentication mechanisms.

   Reply code 530 [SMTP-AUTH] is used for this purpose.

5.  Recommended Actions

   The MSA SHOULD do all of the following:

5.1.  Enforce Address Syntax

   An MSA SHOULD reject messages with illegal syntax in a sender or
   recipient SMTP envelope address.

   If the MSA examines or alters the message text in way, except to add
   trace header fields, it SHOULD reject messages with illegal address
   syntax in address header fields.

   Reply code 501 is to be used to reject a MAIL or RCPT command that
   contains a detectably improper address.

   When addresses are resolved after submission of the message body,
   reply code 554 (with a suitable enhanced status code from
   [SMTP-CODES]) is used after end-of-data, if the message contains
   invalid addresses in the header.

5.2.  Log Errors

   The MSA SHOULD log message errors, especially apparent
   misconfigurations of client software.

   It can be very helpful to notify the administrator when problems are
   detected with local mail clients.  This is another advantage of
   distinguishing submission from relay: system administrators might be
   interested in local configuration problems, but not in client
   problems at other sites.

   Note that it is important to impose limits on such logging to prevent
   certain forms of denial of service (DoS) attacks.






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6.  Optional Actions

   The MSA MAY do any of the following:

6.1.  Enforce Submission Rights

   The MSA MAY issue an error response to a MAIL command if the address
   in MAIL FROM appears to have insufficient submission rights, or is
   not authorized with the authentication used (if the session has been
   authenticated).

   Reply code 550 with an appropriate enhanced status code per
   [SMTP-CODES], such as 5.7.1, is used for this purpose.

6.2.  Enforce Permissions

   The MSA MAY issue an error response to a RCPT command if inconsistent
   with the permissions given to the user (if the session has been
   authenticated).

   Reply code 550 with an appropriate enhanced status code per
   [SMTP-CODES], such as 5.7.1, is used for this purpose.

6.3.  Check Message Data

   The MSA MAY issue an error response to the DATA command or send a
   failure result after end-of-data if the submitted message is
   syntactically invalid, or seems inconsistent with permissions given
   to the user (if known), or violates site policy in some way.

   Reply code 554 is used for syntactic problems in the data.  Reply
   code 501 is used if the command itself is not syntactically valid.
   Reply code 550 with an appropriate enhanced status code per
   [SMTP-CODES] (such as 5.7.1) is used to reject based on the
   submitting user.  Reply code 550 with an appropriate enhanced status
   code (such as 5.7.0) is used if the message violates site policy.

6.4.  Support for the Postmaster Address

   If appropriate under local conditions and to facilitate conformance
   with the "postmaster" requirements of [SMTP-MTA], the MSA MAY permit
   a reduced degree of authentication for mail addressed to the
   "postmaster" (or one of its alternate spelling forms, see
   [SMTP-MTA]), in one or more domains, as compared to requirements
   enforced for other addresses.  Among other benefits, this provides an
   address of last resort that can be used by authorized users to report
   problems that otherwise prevent them from submitting mail.




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7.  Interaction with SMTP Extensions

   The following table lists the current standards-track and
   Experimental SMTP extensions.  Listed are the EHLO keyword, name, an
   indication as to the use of the extension on the submit port, and a
   reference:

Keyword        Name                        Submission  Reference
----------     --------------------------  ----------  ----------------
PIPELINING     Pipelining                    SHOULD    [PIPELINING]
ENHANCEDSTATUSCODES  Enhanced Status Codes   SHOULD    [CODES-EXTENSION]
ETRN           Extended Turn                 MUST NOT  [ETRN]
 ...           Extended Codes                SHOULD    [SMTP-CODES]
DSN            Delivery Status Notification  SHOULD    [DSN]
SIZE           Message size                  MAY       [SIZE]
 ...           521 reply code                MUST NOT  [521REPLY]
CHECKPOINT     Checkpoint/Restart            MAY       [CHECKPOINT]
BINARYMIME     Binary MIME                   MAY       [CHUNKING]
CHUNKING       Chunking                      MAY       [CHUNKING]
8BITMIME       Use 8-bit data                SHOULD    [8BITMIME]
AUTH           Authentication                MUST      [SMTP-AUTH]
STARTTLS       Start TLS                     MAY       [Start-TLS]
NO-SOLICITING  Notification of no soliciting MAY       [Msg-Track]
MTRK           Message Tracking              MAY       [Msg-Track]

   Future SMTP extensions SHOULD explicitly specify if they are valid on
   the Submission port.

   Some SMTP extensions are especially useful for message submission:

   Extended Status Codes [SMTP-CODES] SHOULD be supported and used
   according to [CODES-EXTENSION].  This permits the MSA to notify the
   client of specific configuration or other problems in more detail
   than the response codes listed in this memo.  Because some rejections
   are related to a site's security policy, care should be used not to
   expose more detail to unauthenticated senders than is needed

   [PIPELINING] SHOULD be supported by the MSA.

   [SMTP-AUTH] allows the MSA to validate the authority and determine
   the identity of the submitting user and MUST be supported by the MSA.

   Any references to the DATA command in this memo also refer to any
   substitutes for DATA, such as the BDAT command used with [CHUNKING].







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8.  Message Modifications

   Sites MAY modify submissions to ensure compliance with standards and
   site policy.  This section describes a number of such modifications
   that are often considered useful.

   NOTE:  As a matter of guidance for local decisions to implement
   message modification, a paramount rule is to limit such actions to
   remedies for specific problems that have clear solutions.  This is
   especially true with address elements.  For example, indiscriminately
   appending a domain to an address or element that lacks one typically
   results in more broken addresses.  An unqualified address must be
   verified to be a valid local part in the domain before the domain can
   be safely added.

   Any message forwarded or delivered by the MSA MUST conform to the
   requirements of [SMTP-MTA] and [MESSAGE-FORMAT].

8.1.  Add 'Sender'

   The MSA MAY add or replace the 'Sender' field, if the identity of the
   sender is known and this is not given in the 'From' field.

   The MSA MUST ensure that any address it places in a 'Sender' field is
   in fact a valid mail address.

8.2.  Add 'Date'

   The MSA MAY add a 'Date' field to the submitted message, if it lacks
   it, or correct the 'Date' field if it does not conform to
   [MESSAGE-FORMAT] syntax.

8.3.  Add 'Message-ID'

   The MSA SHOULD add or replace the 'Message-ID' field, if it lacks it,
   or it is not valid syntax (as defined by [MESSAGE-FORMAT]).  Note
   that a number of clients still do not generate Message-ID fields.

8.4.  Transfer Encode

   The MSA MAY apply transfer encoding to the message according to MIME
   conventions, if needed and not harmful to the MIME type.

8.5.  Sign the Message

   The MSA MAY (digitally) sign or otherwise add authentication
   information to the message.




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8.6.  Encrypt the Message

   The MSA MAY encrypt the message for transport to reflect
   organizational policies.

   NOTE:  To be useful, the addition of a signature and/or encryption by
   the MSA generally implies that the connection between the MUA and MSA
   must itself be secured in some other way, for example, by operating
   inside of a secure environment, by securing the submission connection
   at the transport layer, or by using an [SMTP-AUTH] mechanism that
   provides for session integrity.

8.7.  Resolve Aliases

   The MSA MAY resolve aliases (CNAME records) for domain names, in the
   SMTP envelope and optionally in address fields of the header, subject
   to local policy.

   NOTE:  Unconditionally resolving aliases could be harmful.  For
   example, if www.example.net and ftp.example.net are both aliases for
   mail.example.net, rewriting them could lose useful information.

8.8.  Header Rewriting

   The MSA MAY rewrite local parts and/or domains in the SMTP envelope,
   and optionally in address fields of the header, according to local
   policy.  For example, a site may prefer to rewrite 'JRU' as
   'J.Random.User' in order to hide login names, and/or to rewrite
   'squeaky.sales.example.net' as 'zyx.example.net' to hide machine
   names and make it easier to move users.

   However, only addresses, local-parts, or domains which match specific
   local MSA configuration settings should be altered.  It would be very
   dangerous for the MSA to apply data-independent rewriting rules, such
   as always deleting the first element of a domain name.  So, for
   example, a rule that strips the left-most element of the domain, if
   the complete domain matches '*.foo.example.net', would be acceptable.

   The MSA MUST NOT rewrite a forward-pointing (destination) address in
   a way that violates the constraints of [SMTP-MTA] on modifications of
   local-parts.

9.  Security Considerations

   Separation of submission and relay of messages allows a site to
   implement different policies for the two types of services, including
   requiring use of additional security mechanisms for one or both.  It
   can do this in a way which is simpler, both technically and



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   administratively.  This increases the likelihood that policies will
   be applied correctly.

   Separation also can aid in tracking and preventing unsolicited bulk
   email.

   For example, a site could configure its mail servers such that the
   MSA requires authentication before accepting a message, and the MTA
   rejects all RCPT commands for non-local users.  This can be an
   important element in a site's total email security policy.

   If a site fails to require any form of authorization for message
   submissions (see section 3.3 for discussion), it is allowing open use
   of its resources and name; unsolicited bulk email can be injected
   using its facilities.

   Section 3 includes further discussion of issues with some
   authentication methods.

   Section 5.2 includes a cautionary note that unlimited logging can
   enable certain forms of denial of service attacks.

10.  IANA Considerations

   The registration for port 587 has been updated to refer to this memo
   rather than RFC 2476.

11.  Acknowledgements

   Nathaniel Borenstein and Barry Leiba were instrumental in the
   development of this update to RFC 2476.

   The original memo (RFC 2476) was developed in part based on comments
   and discussions which took place on and off the IETF-Submit mailing
   list.  The help of those who took the time to review that document
   and make suggestions is appreciated, especially that of Dave Crocker,
   Ned Freed, Keith Moore, John Myers, and Chris Newman.

   Special thanks to Harald Alvestrand, who got this effort started.












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12.  Normative References

   [ESMTP]           Klensin, J., Freed, N., Rose, M., Stefferud, E.,
                     and D. Crocker, "SMTP Service Extensions", STD 10,
                     RFC 1869, November 1995.

   [KEYWORDS]        Bradner, S., "Key words for use in RFCs to Indicate
                     Requirement Levels", BCP 14, RFC 2119, March 1997.

   [SMTP-MTA]        Postel, J., "Simple Mail Transfer Protocol", STD
                     10, RFC 821, August 1982.

                     Partridge, C., "Mail routing and the domain
                     system", STD 10, RFC 974, January 1986.

                     Braden, R., "Requirements for Internet Hosts -
                     Application and Support", STD 3, RFC 1123, October
                     1989.

                     Klensin, J., "Simple Mail Transfer Protocol", RFC
                     2821, April 2001.

13.  Informative References

   [521REPLY]        Durand, A. and F. Dupont, "SMTP 521 Reply Code",
                     RFC 1846, September 1995.

   [8BITMIME]        Klensin, J., Freed, N., Rose, M., Stefferud, E.,
                     and D. Crocker, "SMTP Service Extension for 8bit-
                     MIMEtransport", RFC 1652, July 1994.

   [CHECKPOINT]      Crocker, D., Freed, N., and A. Cargille, "SMTP
                     Service Extension for Checkpoint/Restart", RFC
                     1845, September 1995.

   [CHUNKING]        Vaudreuil, G., "SMTP Service Extensions for
                     Transmission of Large and Binary MIME Messages",
                     RFC 3030, December 2000.

   [CODES-EXTENSION] Freed, N., "SMTP Service Extension for Returning
                     Enhanced Error Codes", RFC 2034, October 1996.

   [DSN]             Moore, K., "Simple Mail Transfer Protocol (SMTP)
                     Service Extension for Delivery Status Notifications
                     (DSNs)", RFC 3461, January 2003.

   [ETRN]            De Winter, J., "SMTP Service Extension for Remote
                     Message Queue Starting", RFC 1985, August 1996.



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   [IMAP4]           Crispin, M., "INTERNET MESSAGE ACCESS PROTOCOL -
                     VERSION 4rev1", RFC 3501, March 2003.

   [IPSEC]           Kent, S. and R. Atkinson, "Security Architecture
                     for the Internet Protocol", RFC 2401, November
                     1998.

   [MESSAGE-FORMAT]  Crocker, D., "Standard for the format of ARPA
                     Internet text messages", STD 11, RFC 822, August
                     1982.

                     Braden, R., "Requirements for Internet Hosts -
                     Application and Support", STD 3, RFC 1123, October
                     1989.

                     Resnick, P., "Internet Message Format", RFC 2822,
                     April 2001.

   [Msg-Track]       Allman, E. and T. Hansen, "SMTP Service Extension
                     for Message Tracking", RFC 3885, September 2004.

   [PIPELINING]      Freed, N., "SMTP Service Extension for Command
                     Pipelining", STD 60, RFC 2920, September 2000.

   [POP3]            Myers, J. and M. Rose, "Post Office Protocol -
                     Version 3", STD 53, RFC 1939, May 1996.

   [SIZE]            Klensin, J., Freed, N., and K. Moore, "SMTP Service
                     Extension for Message Size Declaration", STD 10,
                     RFC 1870, November 1995.

   [SMTP-AUTH]       Myers, J., "SMTP Service Extension for
                     Authentication", RFC 2554, March 1999.

   [SMTP-CODES]      Vaudreuil, G., "Enhanced Mail System Status Codes",
                     RFC 3463, January 2003.

   [Start-TLS]       Hoffman, P., "SMTP Service Extension for Secure
                     SMTP over Transport Layer Security", RFC 3207,
                     February 2002.











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Authors' Addresses

   Randall Gellens
   QUALCOMM Incorporated
   5775 Morehouse Drive
   San Diego, CA  92121-2779
   USA

   EMail: rg+ietf@qualcomm.com


   John C. Klensin
   1770 Massachusetts Ave, #322
   Cambridge, MA 02140
   USA

   EMail: john+ietf@jck.com


































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RFC 4409              Message Submission for Mail             April 2006


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