[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]
new drafts of draft-ietf-msgtrk-smtpext-03, trkstat-03
I'll be formally submitting these probably next week, but I wanted to
give folks a chance to catch anything bone-headed first.
eric
Internet Draft E. Allman
draft-ietf-msgtrk-smtpext-03.txt Sendmail, Inc.
Valid for six months T. Hansen
Updates: RFC 1891 AT&T Laboratories
October 12, 2001
SMTP Service Extension
for Message Tracking
<draft-ietf-msgtrk-smtpext-03.txt>
Status of This Memo
This document is an Internet-Draft and is in full conformance
with all provisions of Section 10 of RFC2026. Internet-Drafts are
working documents of the Internet Engineering Task Force (IETF), its
areas, and its working groups. Note that other groups may also dis-
tribute working documents as Internet-Drafts.
Internet-Drafts are draft documents valid for a maximum of six
months and may be updated, replaced, or obsoleted by other documents
at any time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress."
The list of current Internet-Drafts can be accessed at:
http://www.ietf.org/ietf/1id-abstracts.txt
The list of Internet-Draft Shadow Directories can be accessed at:
http://www.ietf.org/shadow.html
This document is a submission by the MSGTRK Working Group of the
Internet Engineering Task Force (IETF). Comments should be submitted
to the ietf-msgtrk@xxxxxxx mailing list. An archive of the mailing
list may be found at
http://www.imc.org/ietf-msgtrk/index.html
Distribution of this memo is unlimited.
1. Abstract
This memo defines an extension to the SMTP service whereby a
client may mark a message for future tracking.
Internet Draft Message Tracking ESMTP Extension October 12, 2001
2. Other Documents and Conformance
The model used for Message Tracking is described in [DRAFT-
MTRK-MODEL].
Doing a Message Tracking query is intended as a "last resort"
mechanism. Normally, Delivery Status Notifications (DSNs) [RFC-
DSN-SMTP] and Message Disposition Notifications (MDNs) [RFC-MDN]
would provide the primary delivery status. Only if the message is
not received, or there is no response from either of these mecha-
nisms should a Message Tracking query be issued.
The definition of the base64 token is imported from section
6.8 of [RFC-MIME].
Syntax notation in this document conforms to [RFC-ABNF].
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 in RFC 2119
[RFC-KEYWORDS].
3. SMTP Extension Overview
The Message Tracking SMTP service extension uses the SMTP ser-
vice extension mechanism described in [RFC-ESMTP]. The following
service extension is hereby defined:
(1) The name of the SMTP service extension is "Message Track-
ing".
(2) The EHLO keyword value associated with this extension is
"MTRK".
(3) No parameters are allowed with this EHLO keyword value.
Future documents may extend this specification by specifying
options.
(4) One optional parameter using the keyword "MTRK" is added to
the MAIL command. In addition, the ENVID parameter of the
MAIL command (as defined in RFC 1891 sections 5.4) MUST be
supported, with extensions as described below. The ORCPT
parameter of the RCPT command (as defined in RFC 1891 sec-
tion 5.2) MUST also be supported.
(5) The maximum length of a MAIL command line is increased by 40
characters by the possible addition of the MTRK keyword and
value. Note that the 507 character extension of RCPT com-
mands for the ORCPT parameter and the 107 character exten-
sion of MAIL commands for the ENVID parameter as mandated by
RFC 1891 [RFC-DSN-SMTP] must also be included.
(6) No SMTP verbs are defined by this extension.
Allman & Hansen [Page 2]
Internet Draft Message Tracking ESMTP Extension October 12, 2001
4. The Extended MAIL Command
The extended MAIL command is issued by an SMTP client when it
wishes to inform an SMTP server that message tracking information
should be retained for future querying. The extended MAIL command
is identical to the MAIL command as defined in [RFC-SMTP], except
that MTRK, ORCPT, and ENVID parameters appear after the address.
4.1. The MTRK parameter to the ESMTP MAIL command
Any sender wishing to request the retention of data for
further tracking of message must first tag that message as
trackable by creating two values A and B:
A = some-large-random-number
B = SHA1(A)
The large random number A is calculated on a host-dependent
basis. See [RFC-RANDOM] for a discussion of choosing good ran-
dom numbers. This random number MUST be at least 128 bits but
MUST NOT be more than 1024 bits.
The 128-bit hash B of A is then computed using the SHA-1
algorithm as described in [NIST-SHA1].
The sender then base64 encodes value B and passes that
value as the mtrk-certifier on the MAIL command:
mtrk-parameter = "MTRK=" mtrk-certifier [ ":" mtrk-timeout ]
mtrk-certifier = base64 ; authenticator
mtrk-timeout = 1*9digit ; seconds until timeout
A is stored in the originator's tracking database to vali-
date future tracking requests as described in [DRAFT-MTRK-MTQP].
B is stored in tracking databases of compliant receiver MTAs and
used to authenticate future tracking requests.
The mtrk-timeout field indicates the number of seconds that
the client requests that this tracking information be retained
on intermediate servers, as measured from the initial receipt of
the message at that server. Servers MAY ignore this value if it
violates local policy. In particular, servers MAY silently
enforce an upper limit to how long they will retain tracking
data; this limit MUST be at least one day.
If no mtrk-timeout field is specified then the server
should use a local default. This default SHOULD be 8-10 days
and MUST be at least one day. Notwithstanding this clause, the
information MUST NOT be expired while the message remains in the
queue for this server: that is, an MTQP server MUST NOT deny
knowledge of a message while that same message sits in the MTA
queue.
If the message is relayed to another compliant SMTP server,
the MTA acting as the client SHOULD pass an mtrk-timeout field
Allman & Hansen [Page 3]
Internet Draft Message Tracking ESMTP Extension October 12, 2001
equal to the remaining life of that message tracking informa-
tion. Specifically, the tracking timeout is decremented by the
number of seconds the message has lingered at this MTA and then
passed to the next MTA. If the decremented tracking timeout is
less than or equal to zero, the entire MTRK parameter MUST NOT
be passed to the next MTA; essentially, the entire tracking path
is considered to be lost at that point.
See [RFC-DELIVERYBY] section 4 for an explanation of why a
timeout is used instead of an absolute time.
4.2. Use of ENVID
To function properly, Message Tracking requires that each
message have a unique identifier that is never reused by any
other message. For that purpose, if the MTRK parameter is
given, an ENVID parameter MUST be included, and the syntax of
ENVID from RFC 1891 section 5.4 is extended as follows:
envid-parameter = "ENVID=" unique-envid
unique-envid = local-envid "@" fqhn
local-envid = xtext
fqhn = xtext
The unique-envid MUST be chosen in such a way that the same
ENVID will never be used by any other message sent from this
system or any other system. In most cases, this means setting
fqhn to be the fully qualified host name of the system generat-
ing this ENVID, and local-envid to an identifier that is never
re-used by that host.
Any resubmissions of this message into the message trans-
mission system MUST assign a new ENVID. In this context,
"resubmission" includes forwarding or resending a message from a
user agent, but does not include MTA-level aliasing or forward-
ing where the message does not leave and re-enter the message
transmission system.
4.3. Forwarding Tracking Certifiers
MTAs SHOULD forward unexpired tracking certifiers to com-
pliant mailers as the mail is transferred during regular hop-to-
hop transfers. If the "downstream" MTA is not MTRK-compliant,
then the MTRK= parameter MUST be deleted. If the downstream MTA
is DSN-compliant, then the ENVID and ORCPT parameters MUST NOT
be deleted.
If aliasing, forwarding, or other redirection of a recipi-
ent occurs, and the result of the redirection is exactly one
recipient, then the MTA SHOULD treat this as an ordinary hop-to-
hop transfer and forward the MTRK=, ENVID=, and ORCPT= values;
these values MUST NOT be modified.
MTAs MUST NOT copy MTRK certifiers when a recipient is
aliased, forwarded, or otherwise redirected and the redirection
results in more than one recipient. However, an MTA MAY
Allman & Hansen [Page 4]
Internet Draft Message Tracking ESMTP Extension October 12, 2001
designate one of the multiple recipients as the "primary" recip-
ient to which tracking requests shall be forwarded; other
addresses MUST NOT receive tracking certifiers. MTAs MUST NOT
forward MTRK certifiers when doing mailing list expansion.
5. Security Issues
5.1. Denial of service
An attacker could attempt to flood the database of a server
by submitting large numbers of small, tracked messages. In this
case, a site may elect to lower its maximum retention period
retroactively.
5.2. Confidentiality
The mtrk-authenticator value (``A'') must be hard to pre-
dict and not reused.
The originating client must take reasonable precautions to
protect the secret. For example, if the secret is stored in a
message store (e.g., a "Sent" folder), the client must make sure
the secret isn't accessible by attackers, particularly on a
shared store.
Many site administrators believe that concealing names and
topologies of internal systems and networks is an important
security feature. MTAs need to balance such desires with the
need to provide adequate tracking information.
In some cases site administrators may want to treat deliv-
ery to an alias as final delivery in order to separate roles
from individuals. For example, sites implementing ``postmas-
ter'' or ``webmaster'' as aliases may not wish to expose the
identity of those individuals by permitting tracking through
those aliases. In other cases, providing the tracking informa-
tion for an alias is important, such as when the alias points to
the user's preferred public address.
Therefore, implementors are encouraged to provide mecha-
nisms by which site administrators can choose between these
alternatives.
6. Acknowledgements
Several individuals have commented on and enhanced this draft,
including Philip Hazel, Alexey Melnikov, Lyndon Nerenberg, Chris
Newman, and Gregory Neil Shapiro.
7. References
[DRAFT-MTRK-MODEL]
T. Hansen, ``Message Tracking Model and Requirements.''
draft-ietf-msgtrk-model-03.txt. November 2000.
Allman & Hansen [Page 5]
Internet Draft Message Tracking ESMTP Extension October 12, 2001
[DRAFT-MTRK-MTQP]
T. Hansen, ``Message Tracking Query Protocol.'' draft-ietf-
msgtrk-mtqp-01.txt. November 2000.
[RFC-ABNF]
Crocker, D., Editor, and P. Overell, ``Augmented BNF for Syn-
tax Specifications: ABNF'', RFC 2234, November 1997.
[RFC-DELIVERYBY]
D. Newman, ``Deliver By SMTP Service Extension.'' RFC 2852.
June 2000.
[RFC-DSN-REPT]
G. Vaudreuil, ``The Multipart/Report Content Type for the
Reporting of Mail System Administrative Messages.'' RFC 1892.
January 1996.
[RFC-DSN-SMTP]
K. Moore, ``SMTP Service Extension for Delivery Status Notifi-
cations.'' RFC 1891. January 1996.
[RFC-DSN-STAT]
K. Moore and G. Vaudreuil, ``An Extensible Message Format for
Delivery Status Notifications.'' RFC 1894. January 1996.
[RFC-EMSSC]
G. Vaudreuil, ``Enhanced Mail System Status Codes.'' RFC
1893. January 1996.
[RFC-ESMTP]
Rose, M., Stefferud, E., Crocker, D., Klensin, J. and N.
Freed, ``SMTP Service Extensions.'' STD 10, RFC 1869. Novem-
ber 1995.
[RFC-KEYWORDS]
S. Bradner, ``Key words for use in RFCs to Indicate Require-
ment Levels.'' RFC 2119. March 1997.
[RFC-MDN]
R. Fajman, ``An Extensible Message Format for Message Disposi-
tion Notifications.'' RFC 2298. March 1998.
[RFC-MIME]
N. Freed and N. Borenstein, ``Multipurpose Internet Mail
Extensions (MIME) Part One: Format of Internet Message Bod-
ies.'' RFC 2045. November 1996.
[RFC-MSGFMT]
P. Resnick, editor, ``Internet Message Format.'' RFC 2822.
April 2001.
[RFC-RANDOM]
D. Eastlake, S. Crocker, and J. Schiller, ``Randomness Recom-
mendations for Security.'' RFC 1750. December 1994.
Allman & Hansen [Page 6]
Internet Draft Message Tracking ESMTP Extension October 12, 2001
[RFC-RELATED]
E. Levinson, ``The MIME Multipart/Related Content-type.'' RFC
2387. August 1998.
[NIST-SHA1]
NIST FIPS PUB 180-1, ``Secure Hash Standard.'' National
Institute of Standards and Technology, U.S. Department of Com-
merce. May 1994. DRAFT.
[RFC-SMTP]
J. Klensin, editor, ``Simple Mail Transfer Protocol.'' RFC
2821. April 2001.
8. Authors' Addresses
Eric Allman
Sendmail, Inc.
6425 Christie Ave, 4th Floor
Emeryville, CA 94608
U.S.A.
E-Mail: eric@xxxxxxxxxxxx
Phone: +1 510 594 5501
Fax: +1 510 594 5429
Tony Hansen
AT&T Laboratories
Lincroft, NJ 07738
U.S.A.
Phone: +1 732 576 3207
E-Mail: tony@xxxxxxx
Allman & Hansen [Page 7]
Internet Draft E. Allman
draft-ietf-msgtrk-trkstat-03.txt Sendmail, Inc.
Valid for six months October 12, 2001
Updates: RFC 1893
The Message/Tracking-Status MIME Extension
<draft-ietf-msgtrk-trkstat-03.txt>
Status of This Memo
This document is an Internet-Draft and is in full conformance
with all provisions of Section 10 of RFC2026. Internet-Drafts are
working documents of the Internet Engineering Task Force (IETF), its
areas, and its working groups. Note that other groups may also dis-
tribute working documents as Internet-Drafts.
Internet-Drafts are draft documents valid for a maximum of six
months and may be updated, replaced, or obsoleted by other documents
at any time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress."
The list of current Internet-Drafts can be accessed at:
http://www.ietf.org/ietf/1id-abstracts.txt
The list of Internet-Draft Shadow Directories can be accessed at:
http://www.ietf.org/shadow.html
This document is a submission by the MSGTRK Working Group of the
Internet Engineering Task Force (IETF). Comments should be submitted
to the ietf-msgtrk@xxxxxxx mailing list. An archive of the mailing
list may be found at
http://www.imc.org/ietf-msgtrk/index.html
Distribution of this memo is unlimited.
1. Abstract
Message Tracking is expected to be used to determine the sta-
tus of undelivered e-mail upon request. Tracking is used in con-
junction with Delivery Status Notifications [RFC-DSN-SMTP] and Mes-
sage Disposition Notifications [RFC-MDN]; generally, a message
tracking request will be issued only when a DSN or MDN has not been
received within a reasonable timeout period.
This memo defines a MIME [RFC-MIME] content-type for message
tracking status in the same spirit as RFC 1894, ``An Extensible
Message Format for Delivery Status Notifications'' [RFC-DSN-STAT].
Internet Draft Message/Tracking-Status October 12, 2001
It is to be issued upon a request as described in ``Message Track-
ing Query Protocol'' [DRAFT-MTRK-MTQP]. This memo defines only the
format of the status information. An extension to SMTP [RFC-ESMTP]
to label messages for further tracking and request tracking status
is defined in a separate memo [DRAFT-MTRK-SMTPEXT].
2. Other Documents and Conformance
The model used for Message Tracking is described in [DRAFT-
MTRK-MODEL].
Message tracking is intended for use as a "last resort" mecha-
nism. Normally, Delivery Status Notifications (DSNs) [RFC-DSN-
SMTP] and Message Disposition Notifications (MDNs) [RFC-MDN] would
provide the primary delivery status. Only if no response is
received from either of these mechanisms would Message Tracking be
used.
This document is based on [RFC-DSN-STAT]. Sections 1.3 (Ter-
minology), 2.1.1 (General conventions for DSN fields), 2.1.2
("*-type" subfields), and 2.1.3 (Lexical tokens imported from RFC
822) of [RFC-DSN-STAT] are included into this document by refer-
ence. Other sections are further incorporated as described herein.
Syntax notation in this document conforms to [RFC-ABNF].
The following lexical tokens, defined in [RFC-MSGFMT], are
used in the ABNF grammar for MTSNs: atom, CHAR, comment, CR, CRLF,
DIGIT, LF, linear-white-space, SPACE, text. The date-time lexical
token is defined in [RFC-HOSTREQ].
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 in RFC 2119
[RFC-KEYWORDS].
3. Format of a Message Tracking Status Notification
A Message Tracking Status Notification (MTSN) is intended to
be returned as the body of a Message Tracking request [DRAFT-MTRK-
MTQP]. The actual body MUST be a multipart/related [RFC-RELATED]
with type parameter of "message/tracking-status"; each subpart MUST
be of type "message/tracking-status" as described herein. The mul-
tipart/related body can include multiple message/tracking-status
parts if an MTQP server chains requests to the next server; see
[DRAFT-MTRK-MODEL] and [DRAFT-MTRK-MTQP] for more information about
chaining.
3.1. The message/tracking-status content-type
The message/tracking-status content-type is defined as fol-
lows:
Allman [Page 2]
Internet Draft Message/Tracking-Status October 12, 2001
MIME type name: message
MIME subtype name: tracking-status
Optional parameters: none
Encoding considerations: "7bit" encoding is sufficient and
MUST be used to maintain readability
when viewed by non-MIME mail readers.
Security considerations: discussed in section 4 of this memo.
The body of a message/tracking-status is modeled after
[RFC-DSN-STAT]. That body consists of one or more "fields" for-
matted to according to the ABNF of RFC 2822 header "fields" (see
[RFC-MSGFMT]). The per-message fields appear first, followed by
a blank line. Following the per-message fields are one or more
groups of per-recipient fields. Each group of per-recipient
fields is preceded by a blank line. Note that there will be a
blank line between the final per-recipient field and the MIME
boundary, since one CRLF is necessary to terminate the field,
and a second is necessary to introduce the MIME boundary. For-
mally, the syntax of the message/tracking-status content is as
follows:
tracking-status-content =
per-message-fields 1*( CRLF per-recipient-fields )
The per-message fields are described in section 3.2. The per-
recipient fields are described in section 3.3.
3.1.1. General conventions for MTSN fields
Section 2.1.1 (General conventions for DSN fields) of
[RFC-DSN-STAT] is included herein by reference. Notably, the
definition of xtext is identical to that of that document.
3.1.2. *-type subfields
Section 2.1.2 (*-type subfields) of [RFC-DSN-STAT] is
included herein by reference. Notably, the definitions of
address-type, diagnostic-type, and MTA-name type are identi-
cal to that of RFC 1894.
3.2. Per-Message MTSN Fields
Some fields of an MTSN apply to all of the addresses in a
single envelope. These fields may appear at most once in any
MTSN. These fields are used to correlate the MTSN with the
original message transaction and to provide additional informa-
tion which may be useful to gateways.
per-message-fields =
original-envelope-id-field CRLF
reporting-mta-field CRLF
arrival-date CRLF
*( extension-field CRLF )
Allman [Page 3]
Internet Draft Message/Tracking-Status October 12, 2001
3.2.1. The Original-Envelope-Id field
The Original-Envelope-Id field is defined as in section
2.2.1 of [RFC-DSN-STAT]. This field is REQUIRED.
3.2.2. The Reporting-MTA field
The Reporting-MTA field is defined as in section 2.2.2
of [RFC-DSN-STAT]. This field is REQUIRED.
3.2.3. The Arrival-Date field
The Arrival-Date field is defined as in section 2.2.5 of
[RFC-DSN-STAT]. This field is REQUIRED.
3.3. Per-Recipient MTSN fields
An MTSN contains information about attempts to deliver a
message to one or more recipients. The delivery information for
any particular recipient is contained in a group of contiguous
per-recipient fields. Each group of per-recipient fields is
preceded by a blank line.
The syntax for the group of per-recipient fields is as fol-
lows:
per-recipient-fields =
original-recipient-field CRLF
final-recipient-field CRLF
action-field CRLF
status-field CRLF
[ remote-mta-field CRLF ]
[ last-attempt-date-field CRLF ]
[ will-retry-until-field CRLF ]
*( extension-field CRLF )
3.3.1. Original-Recipient field
The Original-Recipient field is defined as in section
2.3.1 of [RFC-DSN-STAT]. This field is REQUIRED.
3.3.2. Final-Recipient field
The required Final-Recipient field is defined as in sec-
tion 2.3.2 of [RFC-DSN-STAT]. This field is REQUIRED.
3.3.3. Action field
The required Action field indicates the action performed
by the Reporting-MTA as a result of its attempt to deliver
the message to this recipient address. This field MUST be
present for each recipient named in the MTSN. The syntax is
as defined in section 2.3.3 of RFC 1894. This field is
REQUIRED.
Allman [Page 4]
Internet Draft Message/Tracking-Status October 12, 2001
Valid actions are:
failed The message could not be delivered. If DSNs
have been enabled, a "failed" DSN should already
have been returned.
delayed The message is currently waiting in the MTA
queue for future delivery. Essentially, this
action means "the message is located, and it is
here."
delivered The message has been successfully delivered to
the final recipient. This includes "delivery"
to a mailing list exploder. It does not indi-
cate that the message has been read. No further
information is available; in particular, the
tracking agent SHOULD NOT attempt further "down-
stream" tracking requests.
expanded The message has been successfully delivered to
the recipient address as specified by the
sender, and forwarded by the Reporting-MTA
beyond that destination to multiple additional
recipient addresses. However, these additional
addresses are not trackable, and the tracking
agent SHOULD NOT attempt further "downstream"
tracking requests.
relayed The message has been delivered into an environ-
ment that does not support message tracking. No
further information is available; in particular,
the tracking agent SHOULD NOT attempt further
"downstream" tracking requests.
transferred The message has been transferred to another
MTRK-compliant MTA. The tracking agent SHOULD
attempt further "downstream" tracking requests.
opaque The message may or may not have been seen by
this system. No further information is avail-
able or forthcoming.
There may be some confusion between when to use
"expanded" versus "delivered". Whenever possible, "expanded"
should be used when the MTA knows that the message will be
sent to multiple addresses. However, in some cases the
delivery occurs to a program which, unknown to the MTA,
causes mailing list expansion; in the extreme case, the
delivery may be to a real mailbox that has the side effect of
list expansion. If the MTA cannot ensure that this delivery
will cause list expansion, it should set the action to
"delivered".
Allman [Page 5]
Internet Draft Message/Tracking-Status October 12, 2001
3.3.4. Status field
The Status field is defined as in RFC 1894 section
2.3.4. A new code is added to RFC 1893 [RFC-EMSSC],
"Enhanced Mail System Status Codes",
X.1.9 Message relayed to non-compliant mailer"
The mailbox address specified was valid, but the mes-
sage has been relayed to a system that does not speak
this protocol; no further information can be pro-
vided.
A 2.1.9 Status field MUST be used exclusively with a
"relayed" Action field. This field is REQUIRED.
3.3.5. Remote-MTA field
The Remote-MTA field is defined as in section Reference
2.3.5 of [RFC-DSN-STAT]. This field MUST NOT be included if
no delivery attempts have been made or if the Action field
has value "opaque". If delivery to some agent other than an
MTA (for example, a Local Delivery Agent) then this field MAY
be included, giving the name of the host on which that agent
was contacted.
3.3.6. Last-Attempt-Date field
The Last-Attempt-Date field is defined as in section
Reference 2.3.7 of [RFC-DSN-STAT]. This field is REQUIRED if
any delivery attempt has been made and the Action field does
not have value "opaque", in which case it will specify when
it last attempted to deliver this message to another MTA or
other Delivery Agent. This field MUST NOT be included if no
delivery attempts have been made.
3.3.7. Will-Retry-Until field
The Will-Retry-Until field is defined as in section Ref-
erence 2.3.8 of [RFC-DSN-STAT]. If the message is not in the
local queue or the Action field has the value ``opaque'' the
Will-Retry-Until field MUST NOT be included; otherwise, this
field SHOULD be included.
3.4. Extension fields
Future extension fields may be defined as defined in sec-
tion 2.4 of [RFC-DSN-STAT].
3.5. Interaction Between MTAs and LDAs
A message that has been delivered to a Local Delivery Agent
(LDA) that understands message tracking (in particular, an LDA
speaking LMTP [RFC-LMTP] that supports the MTRK extension)
SHOULD pass the tracking request to the LDA. In this case, the
Action field for the MTA->LDA exchange will look the same as a
transfer to a compliant MTA; that is, a "transferred" tracking
Allman [Page 6]
Internet Draft Message/Tracking-Status October 12, 2001
status will be issued.
4. Security Issues
4.1. Forgery
Malicious servers may attempt to subvert message tracking
and return false information. This could result in misdirection
or misinterpretation of results.
4.2. Confidentiality
Another dimension of security is confidentiality. There
may be cases in which a message recipient is autoforwarding mes-
sages but does not wish to divulge the address to which the mes-
sages are autoforwarded. The desire for such confidentiality
will probably be heightened as "wireless mailboxes", such as
pagers, become more widely used as autoforward addresses.
MTA authors are encouraged to provide a mechanism which
enables the end user to preserve the confidentiality of a for-
warding address. Depending on the degree of confidentiality
required, and the nature of the environment to which a message
were being forwarded, this might be accomplished by one or more
of:
(a) respond with a "relayed" tracking status when a message is
forwarded to a confidential forwarding address, and dis-
abling further message tracking requests.
(b) declaring the message to be delivered, issuing a "deliv-
ered" tracking status, re-sending the message to the confi-
dential forwarding address, and disabling further message
tracking requests.
The tracking algorithms MUST NOT allow tracking through
list expansions. When a message is delivered to a list, a
tracking request MUST respond with an "expanded" tracking status
and MUST NOT display the contents of the list.
5. Acknowledgements
Several individuals have commented on and enhanced this draft,
including Tony Hansen, Philip Hazel, Alexey Melnikov, Lyndon Neren-
berg, Chris Newman, Gregory Neil Shapiro, and Dan Wing.
6. References
[DRAFT-MTRK-MODEL]
T. Hansen, ``Message Tracking Model and Requirements.''
draft-ietf-msgtrk-model-03.txt. November 2000.
[DRAFT-MTRK-MTQP]
T. Hansen, ``Message Tracking Query Protocol.'' draft-ietf-
msgtrk-mtqp-01.txt. November 2000.
Allman [Page 7]
Internet Draft Message/Tracking-Status October 12, 2001
[DRAFT-MTRK-SMTPEXT]
E. Allman, ``SMTP Service Extension for Message Tracking.''
draft-ietf-msgtrk-smtpext-00.txt. December 2000.
[RFC-ABNF]
Crocker, D., Editor, and P. Overell, ``Augmented BNF for Syn-
tax Specifications: ABNF'', RFC 2234, November 1997.
[RFC-DSN-REPT]
G. Vaudreuil, ``The Multipart/Report Content Type for the
Reporting of Mail System Administrative Messages.'' RFC 1892.
January 1996.
[RFC-DSN-SMTP]
K. Moore, ``SMTP Service Extension for Delivery Status Notifi-
cations.'' RFC 1891. January 1996.
[RFC-DSN-STAT]
K. Moore and G. Vaudreuil, ``An Extensible Message Format for
Delivery Status Notifications.'' RFC 1894. January 1996.
[RFC-EMSSC]
G. Vaudreuil, ``Enhanced Mail System Status Codes.'' RFC
1893. January 1996.
[RFC-ESMTP]
Rose, M., Stefferud, E., Crocker, D., Klensin, J. and N.
Freed, ``SMTP Service Extensions.'' STD 10, RFC 1869. Novem-
ber 1995.
[RFC-HOSTREQ]
R. Braden (ed.), ``Requirements for Internet Hosts -- Applica-
tion and Support.'' STD 3, RFC 1123. October 1989.
[RFC-KEYWORDS]
S. Bradner, ``Key words for use in RFCs to Indicate Require-
ment Levels.'' RFC 2119. March 1997.
[RFC-LMTP]
J. Myers, ``Local Mail Transfer Protocol.'' RFC 2033. Octo-
ber 1996.
[RFC-MDN]
R. Fajman, ``An Extensible Message Format for Message Disposi-
tion Notifications.'' RFC 2298. March 1998.
[RFC-MIME]
N. Freed and N. Borenstein, ``Multipurpose Internet Mail
Extensions (MIME) Part One: Format of Internet Message Bod-
ies.'' RFC 2045. November 1996.
[RFC-MSGFMT]
P. Resnick, editor, ``Internet Message Format.'' RFC 2822.
April 2001.
Allman [Page 8]
Internet Draft Message/Tracking-Status October 12, 2001
[RFC-RELATED]
E. Levinson, ``The MIME Multipart/Related Content-type.'' RFC
2387. August 1998.
7. Author's Address
Eric Allman
Sendmail, Inc.
6425 Christie Ave, 4th Floor
Emeryville, CA 94608
U.S.A.
E-Mail: eric@xxxxxxxxxxxx
Phone: +1 510 594 5501
Fax: +1 510 594 5429
Allman [Page 9]