Inbound

Inbound KumoMTA MX receiver. It accepts external mail, scans with spam (Rspamd), and forwards to inbox via NATS.

Overview

Property	Value
Directory	`apps/backend/inbound`
Docker service	`inbound` (container `reloop-inbound`)
SMTP port	`25`
HTTP port	`8030` (health check)
Stack	KumoMTA · Lua · spam

Quick start

bun docker:up

Health check: http://localhost:8030/health.

Configuration

Key variables in local/docker-compose.yml:

Variable	Default
`INBOUND_HOSTNAME`	`inbound.reloop.sh`
`NATS_URL`	`reloop-nats:4222`
`KUMOMTA_MIN_FREE_SPACE`	`1%`
`KUMOMTA_MIN_FREE_INODES`	`0`
`KUMOMTA_RSPAMD_URL`	`http://reloop-spam:11333/checkv2`
`KUMOMTA_CHECK_RECIPIENT_URL`	`http://host.docker.internal:8011/api/domain`

Commands

Command	Description
`bun docker:up`	Start full Docker stack (includes inbound)
`docker compose -f local/docker-compose.yml up -d inbound`	Start inbound only
`docker logs -f reloop-inbound`	Stream logs
`curl http://localhost:8030/health`	Health check

Architecture

External Sender → Port 25 → Recipient Check → Spam (Rspamd) → NATS → Inbox
                                                         ↘ discard (no SMTP egress)

Layer	Detail
MX reception	Accepts inbound mail on port `25`
Validation	domain service verifies recipients
Spam scan	spam backend scores mail via `/checkv2`
Forwarding	Accepted messages published to NATS for inbox, then assigned to the `null` queue
Receive-only	No SMTP AUTH, no HTTP inject, no outbound delivery; submission is smtp only

Setup

One-command local bootstrap

Port reference

Port 25 and edge conflicts

Inbox

Persists messages from NATS

Domain

Recipient validation API

Spam

Rspamd scan backend for inbound