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Stalwart - A Modern complete suite Email Server

Introduction

Stalwart is an open-source mail and collaboration server designed for the modern internet. Stalwart supports a wide range of protocols including JMAP, IMAP4, POP3, SMTP, CalDAV, CardDAV, and WebDAV, making it a comprehensive solution for managing email, calendars, contacts, file storage, and more. Built in Rust, Stalwart is engineered to be secure, fast, robust, and scalable, capable of running everything from small personal mail servers to large, distributed enterprise deployments.

Stalwart offers a variety of services, storage systems, authentication methods and scalability strategies. We're not covering everything here but just being able to run the service with several usages.

Installation

Stalwart is available as a Docker image, to make it easy to install, we'll use it:

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services:
    stalwart-mail:
        image: stalwartlabs/mail-server:latest
        volumes:
            - ./stalwart-mail:/opt/stalwart-mail
        restart: unless-stopped
        ports:
            - 443:443
            - 8080:8080
            - 25:25
            - 587:587
            - 465:465
            - 143:143
            - 993:993
            - 4190:4190
            - 110:110
            - 995:995

Quick setup

We're going to setup a simple setup with a single user and a single domain.

Create a domain

Setup ACME TLS

Create a user

Configuration

Routes: forward emails

This is a simple feature we can find in Postfix, unfortunately, Stalwart doesn't support this feature out of the box (yet? in version 0.12, it's not available). Instead we have to use the routes feature and Sieve scripts to forward emails to a specific address.

Here is the way to proceed:

  1. Create a user to use the route (user here who has the [email protected] email address)
  2. Prepare the Sieve script to forward emails to a specific address:
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require ["variables", "copy", "vnd.stalwart.expressions", "envelope", "editheader"];

let "i" "0";
while "i < count(envelope.to)" {
  let "redirected" "false";

  if eval "eq_ignore_case(envelope.to[i], '[email protected]')" {
    addheader "Delivered-To" "[email protected]";
    redirect :copy "[email protected]";

    deleteheader :index 1 :is "Delivered-To" "[email protected]";
    let "redirected" "true";
  }

  if eval "!redirected" {
    let "destination" "envelope.to[i]";
    redirect :copy "${destination}";
  }
  let "i" "i+1";
}
discard;
  1. Update the routes configuration to use the Sieve script.

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Relay host

In order to avoid managing the server reputation, we can use a relay host.

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