mailcow vs Mailu vs Mail-in-a-Box in 2026: Which Self-Hosted Mail Server to Choose?

Self-hosting email remains, in 2026, one of the most demanding challenges in self-hosting. Where a Nextcloud or Jellyfin installation might forgive a configuration error, a poorly configured mail server ends up in everyone’s spam folder, or worse, gets blacklisted within hours. The problem isn’t the software: it’s the entire ecosystem (SMTP, IMAP, DKIM, SPF, DMARC, anti-spam, IP reputation) that needs to work together perfectly.

Three projects dominate the scene for those who want to take back control of their mail: mailcow (the complete, powerful Docker suite), Mailu (the modular and lightweight alternative), and Mail-in-a-Box (the “all-in-one” installer aiming for absolute simplicity). We have deployed, configured them on real domains, and subjected them to deliverability tests. Here is an uncompromising comparison to help you choose the right tool based on your skill level and infrastructure.

Comparison Table

| Criteria | mailcow | Mailu | Mail-in-a-Box |

| :--- | :--- | :--- | :--- |

| Architecture | Docker Compose (multi-container) | Docker Compose (modular) | Bash script on dedicated OS |

| Required OS | Any distro with Docker | Any distro with Docker | Ubuntu 22.04 exclusively |

| Min RAM | 6 GB recommended | 2-3 GB | 2 GB (1 GB possible) |

| Webmail included | SOGo (+ calendar, contacts) | Roundcube or Snappymail | Roundcube |

| Anti-spam | Rspamd (excellent) | Rspamd | spamassassin |

| Admin interface | Full-featured web UI | Minimalist web UI | Minimalist web UI |

| Auto DNS | Config assistance | Config assistance | Quasi-automatic |

| CalDAV / CardDAV | Yes (SOGo) | No native support | Yes (lightweight Nextcloud) |

| Learning curve | Medium to high | Medium | Low |

| Updates | Dedicated script | docker compose pull | mailinabox upgrade |

| License | GPLv3 | MIT | CC0 |

| Ideal for | Power users, SMEs | Modular homelab | Motivated beginner |

mailcow: the complete suite that doesn’t compromise

mailcow (mailcow: dockerized) is the reference choice for those who want a professional solution without paying for Google Workspace or Microsoft 365. It is a set of orchestrated Docker containers: Postfix for SMTP, Dovecot for IMAP, Rspamd for anti-spam, SOGo for webmail and calendar/contact synchronization, ClamAV for antivirus, and a particularly polished web administration interface.

What sets mailcow apart is its completeness. Fine-grained management of aliases, multiple domains, quotas, greylisting, domain-specific DKIM policies, backups, mobile push via ActiveSync (z-push), and user-level blacklisting/whitelisting. The Rspamd interface allows you to adjust anti-spam scoring down to the decimal point. For an SME or a power user managing multiple domains, it is the Swiss Army knife.

The downside: mailcow is resource-hungry. The official documentation recommends 6 GB of RAM, and dropping below 4 GB leads to swapping and slowdowns in SOGo and ClamAV. The number of containers (about a dozen) makes debugging more complex, and the disk footprint quickly exceeds several gigabytes. mailcow also wants to manage ports 80 and 443 itself, which requires adaptation if you already have a reverse proxy in place (it is feasible, but not its default mode).

Infrastructure tip: mailcow requires a dedicated IP with a configurable reverse DNS (PTR); otherwise, deliverability collapses. A VPS from a host known for “clean” IP ranges like Hetzner or OVHcloud is essential. Avoid hosts with IP ranges that are regularly blacklisted.

Mailu: modularity for the homelab

Mailu positions itself as the lightweight and modular alternative to mailcow. Also using a Docker Compose architecture, it is designed so that you can choose your components: front-end (internal nginx proxy), admin, IMAP (Dovecot), SMTP (Postfix), anti-spam (Rspamd), optional webmail (Roundcube or Snappymail), optional WebDAV, and optional antivirus.

The benefit of Mailu is that it integrates cleanly into an existing homelab. It can run behind your reverse proxy (Traefik, Caddy, or nginx) without monopolizing ports 80/443, making it much more cohabitable than mailcow when you are already hosting a dozen services. Its configuration relies on a mailu.env file generated by a web assistant, which demystifies the initial installation.

Mailu consumes significantly less than mailcow: 2 to 3 GB of RAM is sufficient for personal use or a small team. In return, the administration interface is more sober, and some of mailcow’s advanced features (native ActiveSync, ultra-fine Rspamd management via UI, integrated backups) are absent or require manual work. Mailu does not provide a CalDAV/CardDAV integration as robust as SOGo: if you want synchronized calendars and contacts, you need to hook up a Radicale or Nextcloud instance alongside it.

Tip: Mailu shines when placed behind a modern reverse proxy. If you don’t have one yet, our tutorial reverse proxy Caddy with Docker gives you an ideal automatic HTTPS base to expose the webmail cleanly.

Mail-in-a-Box: the all-in-one for a painless start

Mail-in-a-Box (MiaB) starts from a radically different philosophy: it is not a Docker stack, but an installation script that transforms a bare Ubuntu 22.04 server into a complete mail server with a single command. It installs and configures Postfix, Dovecot, spamassassin, Roundcube, an authoritative DNS server (nsd), a mini-Nextcloud for CalDAV/CardDAV, and even automatic Let’s Encrypt certificate management.

Its strength is the automation of DNS. MiaB can run its own DNS server and generates all the records for you (MX, SPF, DKIM, DMARC, DNSSEC). The interface tells you exactly which records to paste at your registrar if you prefer to manage DNS elsewhere. For a motivated beginner who wants a functional, deliverable mail server without understanding Postfix in depth, this is the fastest path.

The constraints are strict: MiaB wants a server dedicated solely to itself, running exactly Ubuntu 22.04, with no other services installed. It takes control of the machine. You cannot easily make it coexist with other Docker containers or a shared reverse proxy. It is a mail server, period. The anti-spam (spamassassin) is less effective than Rspamd, and customization is limited by design: MiaB prioritizes convention over configuration.

Use cases: which one is for you?

You manage multiple domains for a small business. mailcow. Multi-domain management, per-user quotas, ActiveSync for team mobiles, and adjustable Rspamd anti-spam make it the most professional solution. Plan for a VPS with at least 6 GB of RAM.

You already have a well-stocked homelab with a reverse proxy. Mailu. It integrates without breaking your existing architecture, consumes little resources, and you retain control over each component. This is the choice for the experienced self-hoster who wants mail among twenty other services.

It’s your first mail server and you want it to work quickly. Mail-in-a-Box. On a dedicated VPS, you will have a deliverable server with DNS included in an hour. Accept in exchange that you cannot tinker with it endlessly.

You just want one or two accounts for personal use. Honestly, ask yourself if it’s worth it: a VPS with good IP reputation, maintenance time, and the risk of blacklisting in case of error. For personal use, MiaB or a minimal Mailu installation are the least painful options. Otherwise, a service like Infomaniak or Proton hosts your sovereign mail without the operational burden.

The real issue with self-hosted email: deliverability

Regardless of the software, the determining factor is not mailcow vs. Mailu, but your IP reputation and DNS configuration. A perfect server on a blacklisted IP will send nothing. All three require the same non-negotiable prerequisites:

• Reverse DNS (PTR) matching your sending domain name. Without it, Gmail and Outlook reject messages.

• SPF, DKIM, DMARC correctly published. All three software packages generate DKIM keys; you must publish the records.

• A non-blacklisted IP. Check tools like MXToolbox before choosing your VPS. IP ranges from some low-cost hosts are burned.

• Open outbound port 25. Many hosts (and most residential gateways) block it by default. Check before paying.

This is why the choice of host often matters more than the choice of software. Hetzner, OVHcloud, and Infomaniak have generally healthy IP ranges and allow reverse DNS configuration. However, expect to have to “warm up” your IP gradually and request port 25 unblocking via ticket with some providers.

Backup and migration

mailcow provides an integrated backup/restore script (backup_and_restore.sh) covering the database, mail, and configuration. Mailu is backed up via Docker volumes (snapshots of the mailu/ directories and the database). MiaB offers integrated encrypted backup (duplicity) configurable to local storage or S3.

In all cases, treat these backups as critical: losing a mail server without a backup means losing years of correspondence. An encrypted off-site backup strategy is essential, as detailed in our guide automatic backup with Restic and Backblaze.

Verdict

There is no universal winner, but clear choices depending on the profile.

• mailcow is the best for those who want a complete, professional, multi-domain mail suite and have a powerful VPS. This is our recommendation for serious use cases and small teams.

• Mailu is the best compromise for the self-hoster who already has a homelab and a reverse proxy: lightweight, modular, and cohabitable. Our choice for experienced homelabbers.

• Mail-in-a-Box is the easiest to set up and the best entry point for discovering self-hosted email on a dedicated server, provided you accept its constraints.

And remember: none of these software packages will compensate for a bad IP or sloppy DNS. Deliverability is 80% of the work.

FAQ

Is self-hosting email in 2026 really realistic?

Yes, but it is not a “set and forget” project like a reverse proxy. The technology is mature (mailcow, Mailu, and MiaB work very well), but maintaining IP reputation and monitoring blacklists requires continuous attention. For critical use, many choose a sovereign mail host rather than full self-hosting.

Why do my emails go to spam even though the config seems correct?

In the vast majority of cases, it is IP reputation or a missing DNS record. Check your PTR (reverse DNS), your SPF, your DKIM signature, and your DMARC policy. Test your score on tools like mail-tester.com: they pinpoint exactly what is wrong. A new IP also needs to be “warmed up” through gradual sending.

Can I run mailcow on the same VPS as my other services?

It is possible but tricky: mailcow wants to manage ports 80/443 by default. You need to adapt it to coexist with an existing reverse proxy, which is not trivial. If you already have a busy homelab, Mailu is designed for this coexistence and will be much easier to integrate.

How much RAM should I plan for?

mailcow: 6 GB recommended, 4 GB absolute minimum. Mailu: 2 to 3 GB for personal use or small teams. Mail-in-a-Box: 2 GB comfortable, works on 1 GB for very light usage. Disabling ClamAV (antivirus) on mailcow and Mailu frees up a lot of memory if you accept this trade-off.

How do I migrate my mail from Gmail or another server?

All three solutions rely on IMAP. The imapsync tool allows you to copy an entire mailbox from a source server to the new server, including folders and messages. mailcow even offers an IMAP synchronization assistant in its administration interface to automate these batch migrations.

Port 25 is blocked by my host, what should I do?

Without an open outbound port 25, your server cannot send mail directly. Request unblocking from your host (often granted via ticket after anti-abuse verification). If that fails, you can route your sends via an authenticated SMTP relay (smarthost) like a transactional service, at the cost of losing some independence.

Related topics

• Alternatives to Google Workspace in self-hosted

• Automatic HTTPS reverse proxy with Caddy and Docker

• Install and secure an Ubuntu VPS from A to Z

• Automatic backup with Restic and Backblaze

Self-hosting your mail means taking back control of an essential part of your digital life, but it also means accepting permanent vigilance regarding deliverability and security. To stay updated on new vulnerabilities, changes in anti-spam policies from major providers, and updates to these tools, subscribe to our Telegram watch bot.