mix
0d98d92642
test / test (push) Waiting to run
Port 25 accepts only configured domains and listed recipients, then forwards to an upstream; the outbound path is unchanged when the flag is off. Co-authored-by: Cursor <cursoragent@cursor.com>
113 lines
4.3 KiB
Markdown
113 lines
4.3 KiB
Markdown
# SelfPost — product boundaries
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**What this file is.** Stable product definition for SelfPost v1.0: purpose,
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deployment assumptions, explicit out-of-scope items, and the multi-domain
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model. User-facing overview in [README.md](../README.md); install and operations
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in [guide.md](guide.md); as-built technical detail in
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[architecture.md](architecture.md).
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---
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## Purpose
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SelfPost is a self-hosted **outbound SMTP relay** with a web control panel,
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shipped as a single Docker image. It sends mail directly to the internet from
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your own IP with per-domain DKIM signing.
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**Primary workflow:** configure the relay once (domains, DKIM, SASL
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applications), then point scripts and apps at the SMTP endpoint. SelfPost
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delivers as the configured sending domain.
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---
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## Deployment context (fixed assumptions)
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These constraints are intentional; changing them requires an explicit product
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decision:
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1. **VPS or home server** — one image for both. Raspberry Pi and similar boards
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are not a current target but not ruled out forever.
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2. **Send from your own IP (DIY)** — no intermediate relay provider. Requires
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outbound port 25, static IP, and configurable PTR/rDNS from the operator.
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3. **Single container** — Postfix, OpenDKIM, and the panel run under one
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`supervisord` inside one image.
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4. **Panel is internet-facing** — mandatory security requirements in
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[security.md](security.md).
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**Infrastructure the operator provides (not SelfPost features):** unblocked
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outbound TCP 25, static IP, PTR/rDNS, acceptable IP reputation. SelfPost does
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not detect, bypass, or compensate for missing prerequisites; mail simply fails
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to deliver when they are absent.
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---
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## Out of scope
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Explicitly excluded to prevent scope creep:
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- Inbound mail (IMAP/POP3, mailboxes, delivery to user inboxes)
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- Webmail
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- Organisations / tenancy beyond global + domain-admin roles; managing
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**multiple sending domains** under one global administrator is in scope (see
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below)
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- Inbound antispam/antivirus engines (rspamd, ClamAV, etc.) — SelfPost may
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expose a milter hook; it does not ship or start a filter
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- A custom MTA — Postfix is used as-is
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- Dovecot or a full mail stack for SASL — Cyrus SASL (`sasldb2`) only
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The **domain-admin** role ships in the current line (global administrator plus
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domain administrators with assigned domains). The optional **inbound relay**
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(backup-MX / forwarder on port 25) is an agreed 1.x extension — off by default
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behind `INBOUND_RELAY_ENABLE`; it is relay/forward, not IMAP/webmail. Items
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marked *candidate* in the
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[roadmap](roadmap.md) require explicit approval before coding (including
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**send-log retention in Settings**, **30-day send statistics**, and **auto
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level-2 rate limits** — see linked plans there).
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---
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## Multi-domain model
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SelfPost is a **multi-domain outbound relay**. Two linked entities:
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### Sending domain
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Example: `example.com`. Has its own DKIM key and selector.
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### Application (account)
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A SASL login/password bound to **one** domain. A domain may have several
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applications (e.g. newsletter vs alerts), each with its own credentials, but
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each may send **only from its own domain**, never from another.
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### From-address mode (per application)
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Set when creating or editing an application:
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1. **Any address in the domain** — `*@example.com` (wildcard in
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`smtpd_sender_login_maps`).
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2. **Explicit address list** — only listed From addresses within the domain;
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anything else is rejected even if it belongs to the same domain.
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In both modes the From address must belong to the application's domain.
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### What the panel manages per domain
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- DKIM key + selector (shared by all applications on that domain)
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- One or more applications (SASL credentials + From mode + optional rate limits)
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- DNS guidance (DKIM TXT; reminders for SPF/DMARC)
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Adding a domain does **not** create an application automatically.
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### Lifecycle
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- **Add domain** — record, DKIM key, DNS instructions; no application yet.
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- **Add application** — SASL pair (password shown once), From mode, map entries,
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`postfix reload`.
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- **Delete domain** — removes DKIM key and **all** its applications.
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- **Delete application** — removes only that app's SASL and map entries.
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This is not multi-tenancy; it is one owner (or a small team with global and
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domain-scoped roles) operating several sending domains with independent
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application credentials.
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