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The cosmos generator linked a consumer to its provider only through an '<role>' in group_names reference or an explicit provides: name. A hard dependency has neither -- pinning the provider on unconditionally is exactly what removes the Jinja reference the generator was reading -- so web-svc-asset's bond to web-svc-file vanished from the diagram the moment it became binding. Match a service key against the provider's own primary key from the registry, in both directions. Services the role turns off drew a solid 1:1 edge, claiming a mandatory relationship for something that carries nothing at deploy time. They now render as a red 0..0 edge; edge merging gained a real precedence so a provider consumed through two keys stays live when only one is off. Named colour, not hex: a '#' opens an entity code in the mermaid lexer and turns the whole diagram into a parse error on GitHub. Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
87 lines
3.8 KiB
Markdown
87 lines
3.8 KiB
Markdown
# sys-svc-mail-smtp
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## Description
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The `sys-svc-mail-smtp` role configures a **local SMTP relay** using [Postfix](https://www.postfix.org/), listening exclusively on `localhost`.
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It is designed to be used as a fallback when no central Mailu instance is available, enabling applications and system services to send email via `localhost:25` without additional configuration.
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For general background on SMTP, see [SMTP on Wikipedia](https://en.wikipedia.org/wiki/Simple_Mail_Transfer_Protocol).
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For details about Postfix itself, see [Postfix on Wikipedia](https://en.wikipedia.org/wiki/Postfix_(software)).
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## Overview
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This role:
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- Installs Postfix via `pacman` on Arch Linux.
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- Configures it as a **loopback-only relay**, so it:
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- only listens on `127.0.0.1`,
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- does not perform local mailbox delivery,
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- and is safe to use as a simple outbound relay for the local host.
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- Integrates seamlessly with the `sys-svc-mail` and `sys-svc-mail-msmtp` roles in the Infinito.Nexus stack.
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Typically, `sys-svc-mail` decides whether to:
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- Use Mailu (via `sys-svc-mail-msmtp`), **or**
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- Fall back to this role (`sys-svc-mail-smtp`) and send via `localhost`.
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## Cosmos
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The diagram places sys-svc-mail-smtp in the Infinito.Nexus cosmos: the components it deploys (capabilities), the central services it consumes (dependencies), and its outward reach (federation and bridged external networks).
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```mermaid
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flowchart LR
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subgraph role [sys-svc-mail-smtp 💻]
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svc_svc_mail_smtp["svc-mail-smtp"]
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end
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```
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Solid `1:1` edges are fixed relationships; dashed `0..1` edges are conditional (enabled only in matching deployments); red `0..0` edges are turned off in this role. Node markers show the role's deploy modes (💻 host, 🐳 compose, 🐝 swarm); ❌ marks a service that is explicitly turned off, and ⚙️ an Ansible role dependency declared in `meta/main.yml`.
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## Purpose
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The main goals of this role are:
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- Provide a **minimal, secure SMTP relay** for hosts that do not run a full mail stack.
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- Enable `msmtp` (and any other sendmail-compatible client) to send mail by talking to `localhost:25`.
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- Avoid the complexity of a full MTA configuration while still supporting basic outbound notifications.
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This is particularly useful for:
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- Monitoring nodes,
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- Utility hosts,
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- Development or test environments without Mailu.
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## Features
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- 💾 **Postfix Installation on Arch Linux**
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- Uses `community.general.pacman` to install the `postfix` package.
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- 🔒 **Loopback-Only Configuration**
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- Configures `inet_interfaces = loopback-only` to restrict the SMTP daemon to `127.0.0.1`.
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- Defines `mynetworks = 127.0.0.0/8` for safe local relaying.
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- 🚫 **No Local Mailbox Delivery**
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- Sets `local_transport = error: local delivery disabled` to avoid storing mail locally.
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- Focus is purely on **relaying** from localhost rather than full MTA behavior.
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- 🧩 **Integration with Infinito.Nexus**
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- Meant to be driven by `sys-svc-mail`, which decides when to enable this relay.
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- Works hand in hand with `sys-svc-mail-msmtp`, which configures msmtp to talk to `localhost:25` when Mailu is not present.
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## Further Resources
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- SMTP & Mail Transfer:
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- SMTP (Wikipedia): <https://en.wikipedia.org/wiki/Simple_Mail_Transfer_Protocol>
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- Postfix:
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- Official site: <https://www.postfix.org/>
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- Postfix on Wikipedia: <https://en.wikipedia.org/wiki/Postfix_(software)>
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- Related Infinito.Nexus roles:
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- `sys-svc-mail`: central mail orchestration
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- `sys-svc-mail-msmtp`: msmtp client and sendmail replacement
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## Credits
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Implemented by **[Kevin Veen-Birkenbach](https://www.veen.world)**.
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Part of the [Infinito.Nexus Project](https://s.infinito.nexus/code) and maintained by [Kevin Veen-Birkenbach](https://www.veen.world).
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Licensed under the [Infinito.Nexus Community License (Non-Commercial)](https://s.infinito.nexus/license).
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