draft-ietf-ngtrans-ipv6-smtp-requirement-05.txt   draft-ietf-ngtrans-ipv6-smtp-requirement-06.txt 
Internet Engineering Task Force Motonori Nakamura Internet Engineering Task Force Motonori Nakamura
INTERNET-DRAFT Kyoto University INTERNET-DRAFT Kyoto University
Expires: August 28, 2002 Jun-ichiro itojun Hagino Expires: December 28, 2002 Jun-ichiro itojun Hagino
IIJ Research Laboratory IIJ Research Laboratory
February 28, 2002 June 28, 2002
SMTP operational experience in mixed IPv4/IPv6 environements SMTP operational experience in mixed IPv4/IPv6 environements
draft-ietf-ngtrans-ipv6-smtp-requirement-05.txt draft-ietf-ngtrans-ipv6-smtp-requirement-06.txt
Status of this Memo Status of this Memo
This document is an Internet-Draft and is in full conformance with all This document is an Internet-Draft and is in full conformance with all
provisions of Section 10 of RFC2026. provisions of Section 10 of RFC2026.
Internet-Drafts are working documents of the Internet Engineering Task Internet-Drafts are working documents of the Internet Engineering Task
Force (IETF), its areas, and its working groups. Note that other groups Force (IETF), its areas, and its working groups. Note that other groups
may also distribute working documents as Internet-Drafts. may also distribute working documents as Internet-Drafts.
skipping to change at page 1, line 31 skipping to change at page 1, line 32
and may be updated, replaced, or obsoleted by other documents at any and may be updated, replaced, or obsoleted by other documents at any
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To view the list Internet-Draft Shadow Directories, see To view the list Internet-Draft Shadow Directories, see
http://www.ietf.org/shadow.html. http://www.ietf.org/shadow.html.
Distribution of this memo is unlimited. Distribution of this memo is unlimited.
The internet-draft will expire in 6 months. The date of expiration will The internet-draft will expire in 6 months. The date of expiration will
be August 28, 2002. be December 28, 2002.
Abstract Abstract
This document talks about SMTP operational experiences in IPv4/v6 dual This document talks about SMTP operational experiences in IPv4/v6 dual
stack environments. As IPv6-capable SMTP servers are deployed, it has stack environments. As IPv6-capable SMTP servers are deployed, it has
become apparent that certain configurations are necessary in become apparent that certain configurations are necessary in
IPv6-capable MX DNS records for stable dual-stack (IPv4 and IPv6) SMTP IPv6-capable MX DNS records for stable dual-stack (IPv4 and IPv6) SMTP
operation. This document clarifies the problems that exist in the operation. This document clarifies the problems that exist in the
transition period between IPv4 SMTP and IPv6 SMTP. It also defines transition period between IPv4 SMTP and IPv6 SMTP. It also defines
operational requirements for stable IPv4/v6 SMTP operation. operational requirements for stable IPv4/v6 SMTP operation.
This document does not define any new protocol. This document does not define any new protocol.
1. Summary of IPv4 MX operation 1. Introduction
For reference purposes, this section outlines how email message delivery
is performed in an IPv4-only environment [Partridge, 1986] .
DRAFT SMTP in dual stack environments February 2002
In IPv4 SMTP operation, the MX record "example.org." would be registered
as follows:
example.org. IN MX 1 mx1.example.org.
IN MX 10 mx10.example.org.
mx1.example.org. IN A 192.0.2.1
mx10.example.org. IN A 192.0.2.2
When an MTA wishes to deliver a message to a particular destination
(e.g. "foo@example.org"), the MTA sends DNS queries in the following
order:
o Lookup MX record for "example.org.".
o If an MX record is returned, lookup an A record for the right-hand
side of the MX record.
o If a CNAME record is returned, try to chase the CNAME chain.
Eventually an A record will be reached.
NOTE: RFC2181 [Elz, 1997] prohibits MX records from pointing to
CNAME records. However, this was not prohibited in earlier RFCs.
[Partridge, 1986] CNAME chasing logic is mentioned here just for
backwards compatibility. Implementers may want to avoid CNAME
chasing to better conform with RFC2181.
o If the MX lookup fails with NO_DATA, it means that there is no MX
record, but there may be other records (e.g. "example.org.").
Lookup the A record for "example.org.".
o If the MX lookup fails with HOST_NOT_FOUND, it means that there is
no record at all for "example.org.". This results in a delivery
failure.
2. MX records and dual stack SMTP operation Deliveries of mail messages to the final mail drop is not always done by
direct IP communication with submiter and final receiver, and there may
be some intermediate hosts to relay the messages. So it is difficult to
The following sections explain how to make IPv4 SMTP and IPv6 SMTP DRAFT SMTP in dual stack environments June 2002
coexist in a dual-stack environment.
Similar to the way RFC's for IPv6 DNS lookup [Thomson, 1995; Crawford, know at message submission (also at receiver side) that all intermediate
2000] use IN class for both IPv4 and IPv6, IN MX records will be used relay hosts are properly configured. It is not so easy to configure all
for both IPv4 and IPv6. the system with consistency since mail message delivery system is rather
complex on DNS setting than other Internet services. For the transition
state from IPv4 to IPv6, both IPv4 and IPv6 interoperability should be
kept more carefully.
There are several technologies defined for the transition from IPv4 to There are several technologies defined for the transition from IPv4 to
IPv6. This document concentrates on SMTP issues in a dual-stack IPv6. This document concentrates on SMTP issues in a dual-stack
environment. Afterall, there are no special SMTP considerations for environment. Afterall, there are no special SMTP considerations for
translators; If there is SMTP traffic from an IPv6 MTA to an IPv4 MTA translators; If there is SMTP traffic from an IPv6 MTA to an IPv4 MTA
over an IPv6-to-IPv4 translator, the IPv4 MTA will consider this normal over an IPv6-to-IPv4 translator, the IPv4 MTA will consider this normal
IPv4 SMTP traffic. Protocols like IDENT [StJohns, 1993] , however, may IPv4 SMTP traffic. Protocols like IDENT [Johns, 1993] , however, may
require special consideration when translators are used. require special consideration when translators are used.
DRAFT SMTP in dual stack environments February 2002 The following sections explain how to make IPv4 SMTP and IPv6 SMTP
coexist in a dual-stack environment.
This document does not discuss the problems encountered when the sending This document does not discuss the problems encountered when the sending
MTA and the receiving MTA have no common protocol (e.g. the sending MTA MTA and the receiving MTA have no common protocol (e.g. the sending MTA
is IPv4-only while the receiving MTA is IPv6-only). Such a situation is IPv4-only while the receiving MTA is IPv6-only). Such a situation
should be resolved by making either side dual-stack or by making either should be resolved by making either side dual-stack or by making either
side use a protocol translator. side use a protocol translator.
2. Basic DNS resource record definitions for mail routing
Mail messages on the Internet are delivered based on domain name system
generally. MX RRs are looked up to know destination hosts associated
with domain part of a mail addresse. Similar to the way RFC's for IPv6
DNS lookup [Thomson, 1995] use IN class for both IPv4 and IPv6, IN MX
records will be used for both IPv4 and IPv6 on mail message routing,
hosts which have IPv6 transport and want to be delivered with the IPv6
transport must define IPv6 IP addresses for the host name as well as
IPv4 IP addresses.
A MX RR have two data, a preference value and the name of destination
host. IP addresses for the destination host are also looked up to make
SMTP transport [Partridge, 1986] . In IPv4 environment, IPv4 IP
addresses are defined with A RRs.
For example, IPv6 only site may have the following DNS definitions:
example.org. IN MX 1 mx1.example.org.
IN MX 10 mx10.example.org.
mx1.example.org. IN AAAA 3ffe:501:ffff::1
mx10.example.org. IN AAAA 3ffe:501:ffff::2
In transition period from IPv4 to IPv6, there are many IPv4 sites, and
such sites will not have mail interoperability with IPv6 only sites.
For the transition period, every IPv6 sites should have both transport
for each domain part of mail addresses, e.g, for example:
DRAFT SMTP in dual stack environments June 2002
example.org. IN MX 1 mx1.example.org.
IN MX 10 mx10.example.org.
mx1.example.org. IN AAAA 3ffe:501:ffff::1
IN A 192.0.2.1
mx10.example.org. IN AAAA 3ffe:501:ffff::2
IN A 192.0.2.2
But, every host may not support dual stack operation, some host entries
may have only IPv4 or IPv6 RRs:
example.org. IN MX 1 mx1.example.org.
IN MX 10 mx10.example.org.
mx1.example.org. IN AAAA 3ffe:501:ffff::1
mx10.example.org. IN A 192.0.2.1
In the following sections, how sender side operates with IPv4/IPv6
combined RR definitions (section 3), and how receiver side should define
RRs to keep interoperability with both IPv4 and IPv6 Internet (section
4) are considerd.
3. SMTP sender algorithm in a dual-stack environment 3. SMTP sender algorithm in a dual-stack environment
In a dual-stack environment MX records for a domain resemble the In a dual-stack environment MX records for a domain resemble the
following: following:
example.org. IN MX 1 mx1.example.org. example.org. IN MX 1 mx1.example.org.
IN MX 10 mx10.example.org. IN MX 10 mx10.example.org.
mx1.example.org. IN A 192.0.2.1 ; dual-stack mx1.example.org. IN A 192.0.2.1 ; dual-stack
IN AAAA 3ffe:501:ffff::1 IN AAAA 3ffe:501:ffff::1
mx10.example.org. IN AAAA 3ffe:501:ffff::2 ; IPv6 only mx10.example.org. IN AAAA 3ffe:501:ffff::2 ; IPv6 only
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Domains without MX records and failure recovery cases must be handled Domains without MX records and failure recovery cases must be handled
properly as well. properly as well.
The algorithm for an SMTP sender is basically the same as that for an The algorithm for an SMTP sender is basically the same as that for an
IPv4-only sender, but it now includes AAAA lookups of MX records for IPv4-only sender, but it now includes AAAA lookups of MX records for
SMTP-over-IPv6 delivery. IPv4/v6 dual stack destinations should be SMTP-over-IPv6 delivery. IPv4/v6 dual stack destinations should be
treated just like multihomed destinations as described in RFC2821 treated just like multihomed destinations as described in RFC2821
[Klensin, 2001] section 5. When there is no reachable destionation [Klensin, 2001] section 5. When there is no reachable destionation
address record found (for example, the sender MTA is IPv4 only and there address record found (for example, the sender MTA is IPv4 only and there
are no A records available) the case should be treated just like MX are no A records available) the case should be treated just like MX
records without address records. records without address records, and deliveries never fail because of no
known address if other addresses are available related to other MX
records.
DRAFT SMTP in dual stack environments June 2002
; if the sender MTA is IPv4 only, email delivery to a.example.org ; if the sender MTA is IPv4 only, email delivery to a.example.org
; should fail with the same error as deliveries to b.example.org. ; should fail with the same error as deliveries to b.example.org.
a.example.org. IN MX 1 mx1.a.example.org. a.example.org. IN MX 1 mx1.a.example.org.
mx1.a.example.org. IN AAAA 3ffe:501:ffff::1 ; IPv6 only mx1.a.example.org. IN AAAA 3ffe:501:ffff::1 ; IPv6 only
b.example.org. IN MX 1 mx1.b.example.org. b.example.org. IN MX 1 mx1.b.example.org.
mx1.b.example.org. IN HINFO "NO ADDRESS RECORDS" mx1.b.example.org. IN HINFO "NO ADDRESS RECORDS"
(1) Lookup the MX record for the destination domain. If a CNAME record An algorithm for SMTP sender in a dual-stack environment is as follows:
is returned, go to step (1) with the query's result. If any MX
records are returned, go to step (2) with the query's result. If
NO_DATA is returned, there is no MX record. Go to step (3). If
HOST_NOT_FOUND is returned, there is no domain. Raise a permanent
email delivery failure. Finish.
NOTE: the previous section contains a note about MX records that (1) Lookup the MX record for the destination domain. If a CNAME record
point to CNAME records. is returned, go to the top of step (1) with replacing the
destination domain by the query's result. If any MX records are
returned, go to step (2) with the query's result (Implicit MX). If
NO_DATA (i.e. empty answer with NOERROR(0) RCODE) is returned,
there is no MX record but other records (e.g. SOA, NS or A etc.)
may be found. Go to step (3). If HOST_NOT_FOUND (i.e. empty
answer with NXDOMAIN(3) RCODE) is returned, there is no such
domain. Raise a permanent email delivery failure. Finish.
DRAFT SMTP in dual stack environments February 2002 NOTE: Some guard mechanism must required to break circular CNAME
references.
(2) There are multiple MX records. Sort the MX records in ascending (2) Compare each host name in MX records with the name of sending host.
order based on their preference values, and loop over steps (3) to If there is a record which has the same name, drop MX records which
(8). have equal to or larger than preference value of the matched MX
record (including itself). If multiple MX records remain, sort the
MX records in ascending order based on their preference values.
Loop over steps (3) to (9) on each host name in MX records in a
sequence. If no MX records remain, the sending host must be the
primary MX host. Other routing rule should be applied. Finish.
(3) If the sending MTA has IPv4 capability, lookup the A record. Keep (3) If the sending MTA has IPv4 capability, lookup the A record. Keep
the resulting address until step (5). the resulting address until step (5).
(4) If the sending MTA has IPv6 capability, lookup the AAAA record. (4) If the sending MTA has IPv6 capability, lookup the AAAA record.
NOTE: IPv6 addresses for hosts defined by MX records may be
informed in additional information section of DNS querie's result
as well as IPv4 addresses. If there is no additional address
information for the MX hosts, separate queries for A or AAAA
records should be sent. There is no way to query A and AAAA
records at once in current DNS implementation.
(5) If there is no A or AAAA record present, try the next MX record (go (5) If there is no A or AAAA record present, try the next MX record (go
to step (3)). Sort the query's result based on the to step (3)).
implementation's preference of A or AAAA records. If it is
desirable to encourage the transition from IPv4 SMTP to IPv6 SMTP,
AAAA records should take precedence.
(6) For each of the addresses or each part of the list of addresses, NOTE: If one or more address records are found, some MTA
loop over steps (7) to (8). If no reachable destination is found, implementation may sort addresses based on the implementation's
and if a list of MX records is being traversed, try the next MX preference of A or AAAA records. To encourage the transition from
record (go to step (3)). If there is no list of MX records, or if IPv4 SMTP to IPv6 SMTP, AAAA records should take precedence. But
the end of the list of MX records has been reached, raise a this type of sorting is optional.
temporary email delivery failure. Finish.
(7) Try to make a TCP connection to the destination. If unsuccessful, DRAFT SMTP in dual stack environments June 2002
try the next available address. If successful, go to step (8).
(8) Try an SMTP protocol negotiation. If the SMTP protocol negotiation (6) For each of the addresses, loop over steps (7) to (9).
fails with TEMPFAIL (4xx), try the next MX record (go to step (3)).
If successful, SMTP delivery has succeeded. Finish. (7) Try to make a TCP connection to the destination. If successful, go
to step (9).
(8) If unsuccessful and there is another available address, try the
next available address. Go to step (7). If all addresses are not
reachable and if a list of MX records is being traversed, try the
next MX record (go to step (3)). If there is no list of MX
records, or if the end of the list of MX records has been reached,
raise a temporary email delivery failure. Finish.
(9) Try an SMTP protocol negotiation according to RFC2821 [Klensin,
2001] . If a transient failure condision reported, try the next MX
record (go to step (3)). If an error condition reported, raise a
permanent email delivery error, and further MX records are not
tried. Finish. If successful, SMTP delivery has succeeded.
Finish.
4. MX configuration in the recipient domain 4. MX configuration in the recipient domain
4.1. Ensuring reachability for both protocol versions 4.1. Ensuring reachability for both protocol versions
If a site has dual-stack reachability, the site SHOULD configure both A If a site has dual-stack reachability, the site SHOULD configure both A
and AAAA records for its MX hosts. This will help both IPv4 and IPv6 and AAAA records for its MX hosts. This will help both IPv4 and IPv6
senders to reach the site efficiently. senders to reach the site efficiently.
4.2. Reachability between the primary and secondary MX 4.2. Reachability between the primary and secondary MX
When entering MX records in a DNS database in a dual-stack environment, When registering MX records in a DNS database in a dual-stack
reachability between MX hosts must be considered carefully. Suppose all environment, reachability between MX hosts must be considered carefully.
inbound email is to be gathered at the primary MX host, Suppose all inbound email is to be gathered at the primary MX host,
"mx1.example.org.": "mx1.example.org.":
example.org. IN MX 1 mx1.example.org. example.org. IN MX 1 mx1.example.org.
IN MX 10 mx10.example.org. IN MX 10 mx10.example.org.
IN MX 100 mx100.example.org. IN MX 100 mx100.example.org.
If "mx1.example.org" is an IPv6-only node, and the others are IPv4-only If "mx1.example.org" is an IPv6-only node, and the others are IPv4-only
nodes, there is no reachability between the primary MX host and the nodes, there is no reachability between the primary MX host and the
other MX hosts. When email reaches one of the secondary MX hosts, it other MX hosts. When email reaches one of the lower MX hosts, it cannot
be relayed to the primary MX host based on MX preferencing mechanism.
DRAFT SMTP in dual stack environments February 2002
cannot be relayed to the primary MX host.
; This configuration is troublesome. ; This configuration is troublesome.
; No secondary MX can reach mx1.example.org. ; No secondary MX can reach mx1.example.org.
example.org. IN MX 1 mx1.example.org. ; IPv6 only example.org. IN MX 1 mx1.example.org. ; IPv6 only
IN MX 10 mx10.example.org. ; IPv4 only IN MX 10 mx10.example.org. ; IPv4 only
IN MX 100 mx100.example.org. ; IPv4 only IN MX 100 mx100.example.org. ; IPv4 only
The easiest possible configuration is to configure the primary MX host The easiest possible configuration is to configure the primary MX host
as a dual-stack node. By doing so, secondary MX hosts will have no as a dual-stack node. By doing so, secondary MX hosts will have no
DRAFT SMTP in dual stack environments June 2002
problem reaching the primary MX host. problem reaching the primary MX host.
; This configuration works well. ; This configuration works well.
; The secondary MX hosts are able to relay email to the primary MX host ; The secondary MX hosts are able to relay email to the primary MX host
; without any problems. ; without any problems.
example.org. IN MX 1 mx1.example.org. ; dual-stack example.org. IN MX 1 mx1.example.org. ; dual-stack
IN MX 10 mx10.example.org. ; IPv4 only IN MX 10 mx10.example.org. ; IPv4 only
IN MX 100 mx100.example.org. ; IPv6 only IN MX 100 mx100.example.org. ; IPv6 only
There are many other ways to ensure that the primary MX host and the It may not be needed that the primary MX host and lower MX hosts reach
secondary MX hosts can reach one another. For example, it is possible directly one another with IPv4 or IPv6 transport. For example, it is
to configure the secondary MX hosts to route email statically, i.e. possible to establish a routing path with UUCP or an IPv4/v6 translator.
without considering the DNS MX configuration. It is also possible to It is also possible to drop messages into single mailbox with shared
establish an alternate email routing path (e.g. UUCP or an IPv4/v6 storage using NFS or something else offered by a dual-stack server. It
translator) between the secondary MX host and the primary MX host. is receiver site's matter that all messages delivered to each MX hosts
must be reached to recipient's mail drop. In such cases, dual-stack MX
host may not be listed in the MX list.
5. Operational experience 5. Operational experience
Many of the existing IPv6-ready MTA's appear to work in the way Many of the existing IPv6-ready MTA's appear to work in the way
documented in section 3. documented in section 3.
>From past experiments and operational experience, it is known that most >From past experiments and operational experience, it is known that most
of the existing IPv4-only MTA's will not be confused by AAAA records of the existing IPv4-only MTA's will not be confused by AAAA records
that are registered for MX hostnames. No experiments were conducted that are registered for MX hostnames. No experiments were conducted
with A6 records. with A6 records.
There were, however, cases where IPv6-ready MTA's were confused by There were, however, cases where IPv6-ready MTA's were confused by
broken DNS servers. When attempting to canonify a hostname, some broken broken DNS servers. When attempting to canonify a hostname, some broken
name servers return SERVFAIL, a temporary failure, on AAAA record name servers return SERVFAIL (RCODE 2), a temporary failure, on AAAA
lookups. Upon this temporary failure, the email is queued for a later record lookups. Upon this temporary failure, the email is queued for a
attempt. In the interest of IPv4/v6 interoperability, these broken DNS later attempt. In the interest of IPv4/v6 interoperability, these
servers should be fixed. broken DNS servers should be fixed.
6. Open issues 6. Open issues
o How should scoped addresses in email addresses be interpreted on o How should scoped addresses in email addresses be interpreted on
MTA's? As email is relayed between MTA's, interpretation of scoped MTA's? As email is relayed between MTA's, interpretation of scoped
addresses can be different between MTA's. Afterall, intermediate addresses can be different between MTA's. Afterall, intermediate
MTA's may be in different scope zones than the originator. If a MTA's may be in different scope zones than the originator. If a
scoped IPv6 address is returned as the result of a DNS lookup, how scoped IPv6 address is returned as the result of a DNS lookup, how
DRAFT SMTP in dual stack environments February 2002
should MTA's behave? should MTA's behave?
If scoped addresses in ``route-addr'' specifications [Crocker, 1982] If scoped addresses in ``route-addr'' specifications [Crocker, 1982]
are considered, e.g. are considered, e.g.
<@kame.net,@[fec0::1]:itojun@itojun.org> <@kame.net,@[fec0::1]:itojun@itojun.org>
it gets even trickier. Luckily, the route-addr form was obsoleted by it gets even trickier. Luckily, the route-addr form was obsoleted by
DRAFT SMTP in dual stack environments June 2002
RFC2822 [Resnick, 2001] . RFC2822 [Resnick, 2001] .
7. Security considerations 7. Security considerations
As mentioned in the ``Open issues'' section, it could be problematic if As mentioned in the ``Open issues'' section, it could be problematic if
the route-addr email address format is used across multiple scope zones. the route-addr email address format is used across multiple scope zones.
MTA's would need to reject email with improper route-addr email address MTA's would need to reject email with improper route-addr email address
formats. One example of an improper route-addr format is an email from formats. One example of an improper route-addr format is an email from
outside the site border which carries a numeric site-local address in outside the site border which carries a numeric site-local address in
the route-addr format. the route-addr format.
References References
Partridge, 1986. Johns, 1993.
C. Partridge, "Mail routing and the domain system" in RFC974 (January M. St. Johns, "Identification Protocol" in RFC1413 (January 1993).
1986). ftp://ftp.isi.edu/in-notes/rfc974.txt. ftp://ftp.isi.edu/in-notes/rfc1413.txt.
Elz, 1997.
R. Elz and R. Bush, "Clarifications to the DNS Specification" in RFC2181
(July 1997). ftp://ftp.isi.edu/in-notes/rfc2181.txt.
Thomson, 1995. Thomson, 1995.
S. Thomson and C. Huitema, "DNS Extensions to support IP version 6" in S. Thomson and C. Huitema, "DNS Extensions to support IP version 6" in
RFC1886 (December 1995). ftp://ftp.isi.edu/in-notes/rfc1886.txt. RFC1886 (December 1995). ftp://ftp.isi.edu/in-notes/rfc1886.txt.
Crawford, 2000. Partridge, 1986.
M. Crawford, C. Huitema, and S. Thomson, "DNS Extensions to Support IPv6 C. Partridge, "Mail routing and the domain system" in RFC974 (January
Address Aggregation and Renumbering" in RFC2874 (July 2000). 1986). ftp://ftp.isi.edu/in-notes/rfc974.txt.
ftp://ftp.isi.edu/in-notes/rfc2874.txt.
StJohns, 1993.
M. StJohns, "Identification Protocol" in RFC1413 (January 1993).
ftp://ftp.isi.edu/in-notes/rfc1413.txt.
Klensin, 2001. Klensin, 2001.
J. Klensin, Editor, "Simple Mail Transfer Protocol" in RFC2821 (April J. Klensin, Editor, "Simple Mail Transfer Protocol" in RFC2821 (April
2001). ftp://ftp.isi.edu/in-notes/rfc2821.txt. 2001). ftp://ftp.isi.edu/in-notes/rfc2821.txt.
Crocker, 1982. Crocker, 1982.
D. Crocker, "Standard for the format of ARPA Internet text messages" in D. Crocker, "Standard for the format of ARPA Internet text messages" in
RFC822 (August 1982). ftp://ftp.isi.edu/in-notes/rfc822.txt. RFC822 (August 1982). ftp://ftp.isi.edu/in-notes/rfc822.txt.
DRAFT SMTP in dual stack environments February 2002
Resnick, 2001. Resnick, 2001.
P. Resnick, editor, "Internet Message Format" in RFC2822 (April 2001). P. Resnick, editor, "Internet Message Format" in RFC2822 (April 2001).
ftp://ftp.isi.edu/in-notes/rfc2822.txt. ftp://ftp.isi.edu/in-notes/rfc2822.txt.
Change history Change history
00 -> 01 00 -> 01
Corrected the email address notation for source-routed emails, Corrected the email address notation for source-routed emails,
based on a comment from Gregory Neil Shapiro. based on a comment from Gregory Neil Shapiro.
01 -> 02 01 -> 02
Change a reference to refer to RFC2822, not 822. Used Change a reference to refer to RFC2822, not 822. Used
"example.org", not "sample.org". These changes were based on "example.org", not "sample.org". These changes were based on
comments from Arnt Gulbrandsen. Added an ``Operational comments from Arnt Gulbrandsen. Added an ``Operational
experiences'' section. Clarified the case where an MX record experiences'' section. Clarified the case where an MX record
points to a CNAME record, based on comments from Mohsen Souissi. points to a CNAME record, based on comments from Mohsen Souissi.
DRAFT SMTP in dual stack environments June 2002
02 -> 03 02 -> 03
In some cases, IPv6-ready MTA's are troubled by incorrect DNS In some cases, IPv6-ready MTA's are troubled by incorrect DNS
server responses for AAAA queries. This change was based on server responses for AAAA queries. This change was based on
comments from Gregory Neil Shapiro. comments from Gregory Neil Shapiro.
03 -> 04 03 -> 04
Grammar cleanups by JJ Behrens. More text on the delivery error Grammar cleanups by JJ Behrens. More text on the delivery error
cases. cases.
04 -> 05 04 -> 05
Change title, suggested by Alain Durand. Change title, suggested by Alain Durand.
05 -> 06
Section on summary of IPv4 MX operation is deleted (Replaced by
Introduction). Clarify on CNAME chain. Cleanups on sender's
algorithm. Suggested by Patrik Faltstrom.
Acknowledgements Acknowledgements
This draft was written based on discussions with Japanese IPv6 users and This draft was written based on discussions with Japanese IPv6 users and
help from the WIDE research group. Here is a (probably incomplete) list help from the WIDE research group. Here is a (probably incomplete) list
of people who contributed to the draft: Gregory Neil Shapiro, Arnt of people who contributed to the draft: Gregory Neil Shapiro, Arnt
Gulbrandsen, Mohsen Souissi, and JJ Behrens. Gulbrandsen, Mohsen Souissi, and JJ Behrens.
Author's address Author's address
DRAFT SMTP in dual stack environments February 2002
Motonori NAKAMURA Motonori NAKAMURA
Center for Information and Multimedia Studies, Kyoto University Center for Information and Multimedia Studies, Kyoto University
Yoshida-nihonmatsu-cho, Sakyo, Kyoto 606-8501, JAPAN Yoshida-nihonmatsu-cho, Sakyo, Kyoto 606-8501, JAPAN
Tel: +81-75-753-9063 Tel: +81-75-753-9063
Fax: +81-75-753-9056 Fax: +81-75-753-9056
Email: motonori@media.kyoto-u.ac.jp Email: motonori@media.kyoto-u.ac.jp
Jun-ichiro itojun HAGINO Jun-ichiro itojun HAGINO
Research Laboratory, Internet Initiative Japan Inc. Research Laboratory, Internet Initiative Japan Inc.
Takebashi Yasuda Bldg., Takebashi Yasuda Bldg.,
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