Files
relay/doc/source/faq.rst
holger krekel 4ebde2825d feat: support setup without domain, with only an IPv4 address (#963)
* dovecot: enable login names with square brackets

* config: make IPv4-only relays use self-signed TLS certs

* postfix: make delivery for IP-only relays work

* cmdeploy: skip DNS checks for IPv4 only relays

* www: generate dclogin codes for IPv4-only relays

* opendkim: disable DKIM signing on ipv4-only relays

* get delivery working

* get tests working on IPv4 only machine

* doc: document IPv4-only relays

* dns: warn if mail_domain is an IP, instead of checking DNS

* config: validate domains when formatting them

* ci: add cmlxc testing for no-DNS relays

* ci: run no-dns and normal CI in parallel

* retain "config.mail_domain" as the domain part of @ email addresses, so for ipv4 relays  "[1.2.3.4]" and introduce config.ipv4_relay and config.mail_domain_bare helpers.

* ci: migrate from --no-dns to --type ipv4 for cmlxc compatibility

* cleanup dead code, fix docs, fixate cmlxc version

---------

Co-authored-by: missytake <missytake@systemli.org>
2026-05-11 21:52:33 +02:00

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Frequently asked questions
===========================
What is the difference between chatmail relays and classic email servers?
--------------------------------------------------------------------------
A chatmail relay is a minimal Mail Transport Agent (MTA) setup that
goes beyond what classic email servers offer:
- **Zero State:** no private data or metadata collected, messages are auto-deleted, low disk usage
- **Instant/Realtime:** sub-second message delivery, realtime P2P
streaming, privacy-preserving Push Notifications for Apple, Google, and `Ubuntu Touch <https://docs.ubports.com/en/latest/appdev/guides/pushnotifications.html>`_;
- **Security Enforcement**: only strict TLS, DKIM and OpenPGP with minimized metadata accepted
(DKIM is not enforced on :ref:`IP-only relays <iponly>`)
- **Reliable Federation and Decentralization:** No spam or IP reputation checks, federating
depends on established IETF standards and protocols.
How about interoperability with classic email servers?
-------------------------------------------------------
Generally, chatmail relays interoperate well with classic email servers.
However, some chatmail relays may be blocked by Big-Tech email
providers that use intransparent and proprietary techniques for scanning
and looking at cleartext email messages between users, or because they
use questionable IP-reputation systems that break interoperability.
**Chatmail relays instead use and require strong cryptography, allowing
anyone to participate, without having to submit to Big-Tech
restrictions.**
.. _selfhosted:
How are chatmail relays run? Can I run one myself?
--------------------------------------------------
Chatmail relays are designed to be very cheap to run, and are generally
self-funded by respective operators. All chatmail relays are
automatically deployed and updated using `the chatmail relay
repository <https://github.com/chatmail/relay>`__. Chatmail relays are
composed of proven standard email server components, Postfix and
Dovecot, and are configured to run unattended without much maintenance
effort. Chatmail relays happily run on low-end hardware like a Raspberry
Pi.
How trustable are chatmail relays?
----------------------------------
Chatmail relays enforce end-to-end encryption,
and chatmail clients like `Delta Chat <https://delta.chat>`_
enforce end-to-end encryption on their own.
The end-to-end encryption protection includes attached media, user
display names, avatars and group names. What is visible to operators is:
message date, sender and receiver addresses.
Please see the `Delta Chat FAQ on encryption and security <https://delta.chat/en/help#e2ee>`_ for further info.