mixeme
104 lines
3.8 KiB
Markdown
104 lines
3.8 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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- Multi-user panel / organisations / roles — one administrator; managing
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**multiple sending domains** is in scope (see below)
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- Inbound antispam/antivirus (rspamd, ClamAV, etc.)
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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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Future line **2.x.x** (optional inbound relay, domain-admin role) is tracked in
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[roadmap.md](roadmap.md) and requires explicit approval before implementation.
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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 (one admin); it is one owner operating several
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sending domains with independent application credentials.
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