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kevinveenbirkenbachandClaude Opus 5 c55f508e05 feat(readme): draw mandatory and disabled service relations

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>

2026-08-17 18:02:31 +02:00

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sys-svc-mail-smtp

Description

The sys-svc-mail-smtp role configures a local SMTP relay using Postfix, listening exclusively on localhost.
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.

For general background on SMTP, see SMTP on Wikipedia.
For details about Postfix itself, see Postfix on Wikipedia.

Overview

This role:

Installs Postfix via pacman on Arch Linux.
Configures it as a loopback-only relay, so it:
- only listens on 127.0.0.1,
- does not perform local mailbox delivery,
- and is safe to use as a simple outbound relay for the local host.
Integrates seamlessly with the sys-svc-mail and sys-svc-mail-msmtp roles in the Infinito.Nexus stack.

Typically, sys-svc-mail decides whether to:

Use Mailu (via sys-svc-mail-msmtp), or
Fall back to this role (sys-svc-mail-smtp) and send via localhost.

Cosmos

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).

flowchart LR
    subgraph role [sys-svc-mail-smtp 💻]
        svc_svc_mail_smtp["svc-mail-smtp"]
    end

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.

Purpose

The main goals of this role are:

Provide a minimal, secure SMTP relay for hosts that do not run a full mail stack.
Enable msmtp (and any other sendmail-compatible client) to send mail by talking to localhost:25.
Avoid the complexity of a full MTA configuration while still supporting basic outbound notifications.

This is particularly useful for:

Monitoring nodes,
Utility hosts,
Development or test environments without Mailu.

Features

💾 Postfix Installation on Arch Linux
- Uses community.general.pacman to install the postfix package.
🔒 Loopback-Only Configuration
- Configures inet_interfaces = loopback-only to restrict the SMTP daemon to 127.0.0.1.
- Defines mynetworks = 127.0.0.0/8 for safe local relaying.
🚫 No Local Mailbox Delivery
- Sets local_transport = error: local delivery disabled to avoid storing mail locally.
- Focus is purely on relaying from localhost rather than full MTA behavior.
🧩 Integration with Infinito.Nexus
- Meant to be driven by sys-svc-mail, which decides when to enable this relay.
- Works hand in hand with sys-svc-mail-msmtp, which configures msmtp to talk to localhost:25 when Mailu is not present.

Further Resources

SMTP & Mail Transfer:
- SMTP (Wikipedia): https://en.wikipedia.org/wiki/Simple_Mail_Transfer_Protocol
Postfix:
- Official site: https://www.postfix.org/
- Postfix on Wikipedia: https://en.wikipedia.org/wiki/Postfix_(software)
Related Infinito.Nexus roles:
- sys-svc-mail: central mail orchestration
- sys-svc-mail-msmtp: msmtp client and sendmail replacement

Credits

Implemented by Kevin Veen-Birkenbach. Part of the Infinito.Nexus Project and maintained by Kevin Veen-Birkenbach. Licensed under the Infinito.Nexus Community License (Non-Commercial).

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