Deploying and Using Email in Deep Space
draft-many-tiptop-email-01
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| Document | Type | Active Internet-Draft (individual) | |
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| Author | Marc Blanchet | ||
| Last updated | 2026-01-22 | ||
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draft-many-tiptop-email-01
Internet Engineering Task Force M. Blanchet
Internet-Draft Viagenie
Intended status: Informational 22 January 2026
Expires: 26 July 2026
Deploying and Using Email in Deep Space
draft-many-tiptop-email-01
Abstract
This document is an assessment on the email protocols to be used in
deep space and provides recommendations to deploy and use email in
deep space.
Status of This Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering
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and may be updated, replaced, or obsoleted by other documents at any
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material or to cite them other than as "work in progress."
This Internet-Draft will expire on 26 July 2026.
Copyright Notice
Copyright (c) 2026 IETF Trust and the persons identified as the
document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents (https://trustee.ietf.org/
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Please review these documents carefully, as they describe your rights
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provided without warranty as described in the Revised BSD License.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
1.1. Requirements Language . . . . . . . . . . . . . . . . . . 2
1.2. Document and Discussion Locations . . . . . . . . . . . . 3
2. Assessment . . . . . . . . . . . . . . . . . . . . . . . . . 3
3. Deployment Recommendations . . . . . . . . . . . . . . . . . 3
4. Discovering the Next Mail Server . . . . . . . . . . . . . . 4
5. Transport Considerations . . . . . . . . . . . . . . . . . . 5
6. DNS Considerations . . . . . . . . . . . . . . . . . . . . . 5
7. Unwanted Email Considerations . . . . . . . . . . . . . . . . 5
8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 6
9. Security Considerations . . . . . . . . . . . . . . . . . . . 6
10. References . . . . . . . . . . . . . . . . . . . . . . . . . 6
10.1. Normative References . . . . . . . . . . . . . . . . . . 6
10.2. Informative References . . . . . . . . . . . . . . . . . 6
Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . . 7
Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 7
1. Introduction
Deep space communications involve long delays (e.g. Earth to Mars is
4-22 minutes) and intermittent communications, because of orbital
dynamics. As discussed in [I-D.many-tiptop-ip-architecture], IP
packets are stored by forwarders facing intermittent links, instead
of dropping them. So packets travelling from Earth to a celestial
body surface network may take a long time to arrive at destination,
such as minutes, hours, days, weeks. The QUIC transport protocol,
profiled for space delays, is used for reliable transport.
Email protocols such as SMTP and IMAP use TCP as transport, which is
not suitable for space. Moreover, the chatiness of SMTP, which
results in multiple round trips to send an email make it not suitable
over very long delays. This document describes a framework to deploy
and use email in deep space.
1.1. Requirements Language
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
"OPTIONAL" in this document are to be interpreted as described in BCP
14 [RFC2119] [RFC8174] when, and only when, they appear in all
capitals, as shown here.
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1.2. Document and Discussion Locations
The source of this document is located at
https://github.com/marcblanchet/draft-tiptop-email. Comments or
changes are welcomed by filing a PR or an issue against that
repository.
This subject should be discussed on the IETF tiptop working group
mailing list.
2. Assessment
On Internet, to forward an email from the sender to the receipient
server, the SMTP protocol is used over TCP. Prior to sending, the IP
address of the recipient server is found by quering the MX records
and then the IP address records (A, AAAA) of the MX returned values.
SMTP goes through a series of messages between the client and the
server to exchange capabilities, sender and recipient email addresses
and then content of the email. These multiple exchanges result to
multiple RTT to send the whole email. To get its email, a user uses
IMAP or POP, both over TCP, or a web interface. Given TCP is not
appropriate for deep space links[I-D.many-tiptop-usecase], another
email forwarding solution has to be found using a transport protocol
suited for deep space, such as a space profiled
QUIC[I-D.many-tiptop-quic-profile].
A more recent email protocol is JMAP [RFC8621] which uses REST over
HTTP. In deep space, JMAP could be run over HTTP3 over a space
profiled QUIC.
DNS insfrastructure need to be properly deployed and setup to avoid
DNS requests through deep space links as discussed in
[I-D.many-tiptop-dns].
3. Deployment Recommendations
Since TCP is not appropriate, HTTP over QUIC is used to transfer
email over deep space.
On Earth, current SMTP infrastructure is used. For email to be
forwarded from Earth to deep space, the following steps SHOULD be
taken:
* an Earth mail gateway, as the last hop for email on Earth,
receives email by SMTP
* the gateway converts the email to Batch SMTP (BSMTP) MIME object
[RFC2442]
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* the gateway sends the BSMTP object using HTTP3/QUIC to the
corresponding gateway on the celestial body surface network
* the celestial body email gateway receives the BSMTP, disassemble
it and then forwards it using SMTP to the final mail server on the
celestial body network.
Reversely, an email sent from a celestial body surface network to
Earth SHOULD follow these steps:
* email is forwarded to the SMTP gateway on that network
* The SMTP gateway converts the email to Batch SMTP MIME object
[RFC2442]
* The gateway sends it using HTTP3/QUIC to the corresponding gateway
on Earth.
The Earth HTTP endpoint may be statically configured on the celestial
body gateway.
4. Discovering the Next Mail Server
Given the low number of celestial body networks, the use of DNS
lookup may be avoided by having a static map of destination domains
to HTTP endpoints, configured on the Earth mail gateway.
Given the use of HTTP which requires specifying a full URI, the DNS
MX resource record (RR) only provides the hostname of the mail
server, not the full URI.
The DNS URI resource record[RFC7553] SHOULD be used instead of MX
rRR. The URI RR provides similar facility of the MX or SRV records
enabling specifying multiple equivalent mail servers with weights, as
well as multiple servers with different priorities. The service name
used in the query should be "_bsmtp._https". As discussed in
Section 8, the "bsmtp" service name is registered in IANA service
names registry.
For example, the last email hop on Earth receiving an SMTP message to
be forwarded to user1@moon.spaceagency.int have to find the URI and
IP address of the email server on Moon. It queries the DNS for the
URI RR of "_bsmtp._http.moon.spaceagency.in". The DNS response is as
follows:
* _bsmtp._https IN URI 10 1
"https://moonmailgateway1.spaceagency.int/inboundmail"
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* _bsmtp._https IN URI 20 1
"https://moonmailgateway2.spaceagency.int/inboundmail"
The URI RRs received above indicate with the highest priority, noted
with the lowest priority number (10 instead of 20) that the host
moonmailgateway1.spaceagency.int should be contacted first for email
delivery and if not available, then the next priority will be used
(moonmailgateway2.spaceagency.int). The Earth email server will then
query the DNS for IP address records (A and AAAA) of
moonmailgateway1.spaceagency.int. When received, it will connect
moonmailgateway1.spaceagency.int using HTTP3 over QUIC at the full
URI received previously "https://moonmailgateway1.spaceagency.int/
inboundmail".
5. Transport Considerations
As noted in [I-D.many-tiptop-ip-architecture], the transport of BSMTP
email over HTTP on deep space links should be accomplished over QUIC
with proper transport configuration, as specified in
[I-D.many-tiptop-quic-profile].
6. DNS Considerations
For emails sent from Earth, if the DNS is used, the looked up URI
records and their corresponding IP address records should point to
the gateway on the target celestial body network. Those records
should be located or cached on the DNS infrastructure on Earth.
Similarly, if the DNS is used on the celestial body network, it is
assumed that there will be a local DNS infrastructure that has a
cache of the related records, as discussed in [I-D.many-tiptop-dns].
Mail headers such as Received and others contain domain names of the
whole email path, which may contain various hosts on Internet.
Lookup of those names on the celestial body network SHOULD NOT be
done as the local cache cannot contain all the possible mail server
names on Internet.
7. Unwanted Email Considerations
To minimize use of scarce deep space bandwidth, strong anti-spamming
should be done before leaving Earth.
An anti-spamming system on the celestial body network should not rely
on any database or DNS lookup located on Earth.
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8. IANA Considerations
By this specification, the "bsmtp" service name, referring to
[RFC2442] BSMTP specification, is registered as a service name under
RFC6335 policy.
9. Security Considerations
TBD
10. References
10.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997,
<https://www.rfc-editor.org/info/rfc2119>.
[RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
May 2017, <https://www.rfc-editor.org/info/rfc8174>.
[RFC2442] Freed, N., Newman, D., Belissent, J., and M. Hoy, "The
Batch SMTP Media Type", RFC 2442, DOI 10.17487/RFC2442,
November 1998, <https://www.rfc-editor.org/info/rfc2442>.
[RFC7553] Faltstrom, P. and O. Kolkman, "The Uniform Resource
Identifier (URI) DNS Resource Record", RFC 7553,
DOI 10.17487/RFC7553, June 2015,
<https://www.rfc-editor.org/info/rfc7553>.
10.2. Informative References
[RFC8621] Jenkins, N. and C. Newman, "The JSON Meta Application
Protocol (JMAP) for Mail", RFC 8621, DOI 10.17487/RFC8621,
August 2019, <https://www.rfc-editor.org/info/rfc8621>.
[I-D.many-tiptop-usecase]
Blanchet, M., Eddy, W., and M. Eubanks, "IP in Deep Space:
Key Characteristics, Use Cases and Requirements", Work in
Progress, Internet-Draft, draft-many-tiptop-usecase-03, 18
June 2025, <https://datatracker.ietf.org/doc/html/draft-
many-tiptop-usecase-03>.
[I-D.many-tiptop-ip-architecture]
Blanchet, M., Eddy, W., and T. Li, "An Architecture for IP
in Deep Space", Work in Progress, Internet-Draft, draft-
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many-tiptop-ip-architecture-02, 29 September 2025,
<https://datatracker.ietf.org/doc/html/draft-many-tiptop-
ip-architecture-02>.
[I-D.many-tiptop-dns]
Blanchet, M., "Deployment and Use of the Domain Name
System(DNS) in Deep Space", Work in Progress, Internet-
Draft, draft-many-tiptop-dns-01, 28 September 2025,
<https://datatracker.ietf.org/doc/html/draft-many-tiptop-
dns-01>.
[I-D.many-tiptop-quic-profile]
Blanchet, M., "QUIC Profile for Deep Space", Work in
Progress, Internet-Draft, draft-many-tiptop-quic-profile-
01, 23 August 2025,
<https://datatracker.ietf.org/doc/html/draft-many-tiptop-
quic-profile-01>.
Acknowledgements
Initial discussions on this subject were with John Levine who helped
a lot in ironing out many aspects and Pete Resnick.
Author's Address
Marc Blanchet
Viagenie
Canada
Email: marc.blanchet@viagenie.ca
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