Mailcow

What Mailcow actually is

Mailcow is a full mail server suite packaged as a set of Docker containers: Postfix and Dovecot for SMTP and IMAP, SOGo for groupware (calendars, contacts, ActiveSync for phones), Rspamd for spam filtering, ClamAV for antivirus, MariaDB and Redis for state, Nginx plus a web UI for administration, and extras like an Oletools document scanner and full-text indexing. You install it on your own server with a single compose stack and run your own mail — mailboxes, aliases, webmail, the lot — under your own domain and your own IP. It is free software, released under the GNU General Public License v3, developed and maintained by The Infrastructure Company GmbH in Willich, Germany, which also sells the paid support and hosting options around it.

The project lives on GitHub (the mailcow: dockerized repository dates to December 2016 and has accumulated a substantial community — on the order of 13,000+ stars and nearly 2,000 forks at the time of writing) and ships on a monthly release train with occasional revision updates for security fixes. Looking at the public changelog, 2026 has brought a steady cadence: the 2026-10 release landed on 21 October 2026 with component bumps (PHP, SOGo, Nginx), a revision update in May 2026 patched CVE-2026-33278 in Unbound, and the March 2026 release introduced forced two-factor authentication. That cadence matters more than any feature list for software sitting on the internet with port 25 exposed.

What mailcow is not is a hosted product. The open-source suite is self-hosted: you bring the server, the clean IP, the PTR record, and the DNS, and mailcow brings the software. The maintainer's Servercow brand sells two commercial flavours for people who would rather not run it themselves: shared mailcow from EUR 8.90 per month (one domain, 20 mailboxes, up to 50 GB, self-service support) and managed mailcow from EUR 54.90 per month (a dedicated mailcow system in Germany with its own clean IPs, 100 GB expandable to 500 GB, up to 35 ActiveSync devices, and developer support from the mailcow team). We treat those as the commercial backstop for the free core rather than as the product itself.

Pricing: what you really pay

The software costs nothing. Zero euros, zero licence keys, no seat counts, no email volume caps — the only hard limits are physics and your willingness to operate a mail server. That is the honest headline, and it is why mailcow shows up in every self-hosting thread about leaving Google Workspace or Microsoft 365.

The real bill is infrastructure. Mailcow's published minimums are specific: a 1 GHz CPU, 6 GiB of RAM plus 1 GiB of swap with the default configuration, and 20 GiB of disk before you store a single email. The docs are candid about where that goes — ClamAV and the Flatcurve full-text engine are RAM-hungry (you can disable them with SKIP_CLAMD and SKIP_FTS), a single SOGo worker can take roughly 350 MiB before being purged, and the default configuration spawns 20 workers. The project's own guidance: 6 GiB plus swap is fine for most private installs, 8 GiB is recommended for 5 to 10 users, and a company with 15 ActiveSync phones and about 50 concurrent IMAP connections should plan for 16 GiB. A cheap 2-core/8 GiB VPS in the EUR 8–15 per month range covers the typical small deployment, so a personal mail server with mailcow lands at roughly the price of a sandwich per month.

Platform constraints cost money too if you get them wrong. OpenVZ, Virtuozzo, LXC, and NAS appliances are explicitly unsupported — you need full virtualisation (KVM, ESX, Hyper-V). Officially tested operating systems are Debian 11–13, Ubuntu 22.04 or newer, AlmaLinux 8/9, and Rocky Linux 9. And your host must let you send on port 25 and set a reverse DNS record; providers that block port 25 by default will require a support request or a different host.

If you want someone else to hold the pager, the maintainer's own numbers are on the Servercow page: shared mailcow from EUR 8.90 per month and managed mailcow from EUR 54.90 per month, plus paid support contracts and a one-time support-and-licence payment (the "SAL") for people who want to fund development without a subscription. In our view those prices are reasonable for what is effectively maintained-by-the-vendor hosting of the exact open-source stack.

Performance & infrastructure

Mailcow does not sell compute, so there is no vendor benchmark to quote — performance is whatever hardware you put underneath it. What we can say from the documentation is that the suite is a serious piece of engineering rather than a toy wrapper: it spans a webserver, webmailer, ActiveSync, antivirus, antispam, indexing, document scanning, SQL, cache, MDA, MTA, and various web services, and the docs include concrete memory modelling (16 GiB for the 15-phone/50-IMAP scenario above) instead of vague minimums. That kind of specificity is rare and it is why we trust the requirements.

The DNS and network side is where mail servers live or die, and mailcow's prerequisites cover it: correct reverse DNS for your sending IP, SPF/DKIM/DMARC records, MTA-STS support (added in the 2026-09 release train), a stable hostname, working NTP (TOTP two-factor depends on it), and firewall rules moved into the DOCKER-USER chain because Docker rewrites iptables on restart. The docs even flag per-provider quirks, such as Hetzner Cloud's cloud-init IPv6 interface naming. IPv6 is supported in the stack, with a configuration switch for it.

Spam and malware filtering are layered: Rspamd (with a live dashboard showing scores, actions, and throughput), ClamAV with regularly updated signatures on the managed tier, spam and virus learning, and tools like the mail queue view for stuck messages. The security posture has tightened over 2026 — forced 2FA, domain-wide footer fixes, and prompt component bumps when upstreams publish CVEs. The main infrastructure truth is unglamorous and unavoidable: your deliverability depends on your IP's reputation, which you build yourself. A fresh VPS IP with dirty history will land in spam folders no matter how well the software runs.

Where it falls short

The honest cons are operational. Mailcow requires server management expertise: Docker, DNS, reverse DNS, TLS certificates, firewall chains, updates. The project's own docs warn against container platforms and NAS boxes, and the update train expects you to run update.sh regularly. If nobody on your team can debug a Postfix queue at 2 a.m., this is not your product, regardless of the price.

The 6 GiB RAM minimum is real and rules out the cheapest VPS tiers. That is the price of shipping groupware, antivirus, and indexing in one stack; you can trim it by disabling ClamAV and full-text search, but then you have disabled antivirus and full-text search. For one or two mailboxes, a bare MTA on 128 MiB would do — mailcow is deliberately not that.

IP reputation is entirely yours to manage. There is no shared-pool deliverability service bolted on, no vendor negotiating with blocklists on your behalf. The managed tier mitigates this with clean, mail-optimised IPs, but the free tier means you start at zero reputation and earn it.

Support for free users is community-grade (forum, GitHub issues, Telegram). Paid support contracts exist and the maintainer is transparent that they fund development, but there is no SLA behind the free software, and the team has had staffing changes — a departure announcement from a team member appeared on the official blog in 2026. None of that is unusual for open source; it is just the trade you make for EUR 0.

Who should pick this

Our pick for sysadmins, homelabbers, and small organisations that want full control of their email and have someone technical on staff. If your priority is data sovereignty (your mail never leaves hardware you chose), predictable cost, and no per-seat pricing, mailcow is one of the strongest options in the self-hosting category, and it pairs well with any KVM VPS from our /category/vps-providers listings — check /benchmarks for how the underlying hosts perform.

We would also point small companies that like mailcow but not the ops work at managed mailcow: the same suite, run by the people who write it, in Germany, from EUR 54.90 per month. For a 10–20 person shop that is competitive with per-seat hosted mail and keeps you on open software.

We would not pick mailcow for: anyone without Linux server experience, teams that need a credit-backed uptime SLA from a single vendor, one-person projects that only need password-reset emails (use a transactional API for that), or deployments on OpenVZ/LXC budget containers.

Key takeaways

• Mailcow is a free, GPLv3, Docker-based mail suite (Postfix, Dovecot, SOGo, Rspamd, ClamAV) maintained by The Infrastructure Company GmbH in Germany; the project dates to 2016 with monthly releases and prompt security patches.
• True cost is infrastructure: the documented minimum is 1 GHz CPU, 6 GiB RAM plus swap, and 20 GiB disk, with 8 GiB recommended for 5–10 users and 16 GiB for heavy ActiveSync use.
• Commercial escape hatches exist: shared mailcow from EUR 8.90 per month and managed mailcow from EUR 54.90 per month (dedicated system in Germany, clean IPs, developer support).
• Full virtualisation required — OpenVZ, LXC, and NAS devices are explicitly unsupported; port 25 access and reverse DNS control are mandatory.
• Deliverability and IP reputation are entirely self-managed; the software is excellent, the operational burden is real.
• Best for technical users who want email sovereignty at near-zero licence cost; wrong fit for non-technical teams or anyone needing a vendor SLA.

Sources

• https://github.com/mailcow/mailcow-dockerized
• https://docs.mailcow.email/getstarted/prerequisite-system/
• https://www.servercow.de/mailcow?lang=en
• https://mailcow.email/