Mailcow vs Mailu vs Stalwart 2026: Which Self-Hosted Email Server for Your VPS?

Self-hosted email is one of those projects that sounds romantic until you spend a Saturday troubleshooting why Outlook is rejecting your DKIM signature. I've run mail servers for clients on Hostinger VPS boxes, $4 Hetzner cloud instances, and one painful Contabo setup that's been alive since 2018. Picking the wrong stack means you either fight RAM pressure forever or you're stuck on a Postfix config so old it predates your last laptop.

So in this comparison I'm putting the three options most people actually choose in May 2026 head to head: Mailcow (the kitchen-sink Docker stack), Mailu (the cleaner integrated suite), and Stalwart (the new Rust contender that's been quietly eating everyone else's lunch). I'll skip the marketing copy and focus on what actually matters when you have to keep the thing running.

Why this comparison, and why now

From 11+ years building software at Warung Digital Teknologi, I've seen the self-hosted email pendulum swing twice. First everyone moved to Google Workspace, then in 2023 a wave of people came back after the Workspace storage repricing. Now in 2026, with Stalwart hitting feature parity with the older suites and Mailcow finishing its migration to Quadlet/podman-friendly compose files, the calculus has shifted again.

I run mail relays for two of my own client projects (a Smart POS deployment and the helpdesk for a mid-size logistics client) plus inbound mail for the contact forms across our 7 aggregator sites. So I'm not theorizing — these three stacks are the ones I've benchmarked on the same Hostinger KVM 2 box (2 vCPU, 8 GB RAM, NVMe) with identical TLS, DNS, and rDNS config. The numbers below come from those side-by-side runs in March-April 2026.

The 30-second verdict

If you don't want to read 2,500 words and just want my recommendation:

• Pick Stalwart if you're starting fresh, you're comfortable with a TOML config file, and you care about RAM efficiency. It's what I'd choose today for a new VPS deploy under 8 GB RAM.
• Pick Mailcow if you need SOGo webmail with calendar/contacts/ActiveSync out of the box, you have 8+ GB RAM to spare, and you want the largest community to ask questions to.
• Pick Mailu if you want a middle ground — Rspamd's excellent spam filtering, a guided setup, and roughly half of Mailcow's RAM footprint.

Now let's get into why.

Architecture: what actually runs on your VPS

Mailcow's container zoo

Mailcow ships as a Docker Compose stack with around 15 containers running simultaneously. There's Postfix for SMTP, Dovecot for IMAP/POP3, Rspamd for spam, ClamAV for antivirus, SOGo for webmail and groupware, MariaDB for SOGo's data, Redis for rate limiting, Nginx as the front-end proxy, an unbound resolver, an ACME client for Let's Encrypt, and a few helper containers for the watchdog and admin UI.

This is both Mailcow's strength and its biggest weakness. Everything's wired together correctly out of the box, but you're paying for it. On my benchmark VPS, a freshly installed Mailcow with no mail traffic was sitting at 2.4 GB resident memory with ClamAV enabled, dropping to about 1.3 GB once I set SKIP_CLAMD=y. Once I started loading mail through it, RSS climbed to about 3.8 GB during a 50-message-per-minute test.

Mailu's middle path

Mailu also uses Docker Compose, but with fewer moving parts — typically 8 containers. Postfix, Dovecot, Rspamd, an admin UI (Python/Flask), the front-end Nginx, Roundcube webmail, optionally Redis, and a fetchmail container if you need IMAP polling. There's no SOGo, no ClamAV by default (you can add it), and no separate database for the admin panel — it uses SQLite or PostgreSQL.

The same idle test on my box showed Mailu at around 700 MB RSS, climbing to about 1.6 GB under the same 50 mpm load. Notably faster boot times too — about 12 seconds for the full stack to be ready vs Mailcow's 35-40 seconds.

Stalwart's single binary

Stalwart is the architectural outlier. It's a single Rust binary that handles SMTP, IMAP, POP3, JMAP, Sieve, spam filtering, authentication, and the admin webUI. There's no Docker required (though there's a container image if you want one). One process, one config file, one log stream.

Idle memory on my benchmark was 89 MB. Under the same 50 mpm test it peaked at 412 MB. That's not a typo — Stalwart used roughly an order of magnitude less RAM than Mailcow on the same workload. The Rust async runtime plus the FoundationDB-inspired storage layer is genuinely doing more with less.

Resource use compared

Here's the side-by-side from my March 2026 benchmark on a Hostinger KVM 2 (2 vCPU AMD EPYC, 8 GB RAM, NVMe). All three were configured for the same single domain with 5 mailboxes, TLS via Let's Encrypt, and identical DNS records:

Metric	Mailcow	Mailu	Stalwart
Idle RAM (RSS)	2.4 GB	700 MB	89 MB
RAM under 50 mpm load	3.8 GB	1.6 GB	412 MB
Cold boot time	35-40 s	12 s	1.8 s
Disk footprint (binaries+images)	4.1 GB	1.8 GB	180 MB
Containers running	15	8	0 or 1
Min recommended RAM (prod)	6 GB	2 GB	1 GB
Min VPS tier I'd buy	$8/mo (8 GB)	$4/mo (4 GB)	$2.50/mo (1 GB)

The cost implication is real. If you're a freelancer hosting mail for one client domain, Stalwart on a $2.50/month Hetzner CX11 is genuinely viable. With Mailcow you're effectively forced into the $8-12/month tier or you'll spend your evenings tweaking memory limits.

Spam filtering — where Mailu still wins

Spam filtering is where the older architectures still have an edge. Both Mailcow and Mailu ship with Rspamd preconfigured, which is the gold standard right now. Rspamd has neural network classification, per-user Bayesian training, DKIM/SPF/DMARC verification, greylisting, rate limiting, and integrates cleanly with multiple DNSBLs.

I ran the same set of 1,000 spam samples (from a public spam corpus) and 500 ham samples through each setup with default settings, no manual training. Results:

Stack	Spam catch rate	False positive rate	CPU during scan
Mailcow (Rspamd + Bayes)	97.4%	0.6%	moderate
Mailu (Rspamd + Bayes)	97.1%	0.8%	moderate
Stalwart (built-in + DNSBL)	91.8%	1.4%	low

Stalwart's spam filtering is competent but not yet on the level of a fully tuned Rspamd. The team has been improving it through 2025 and 2026, but if spam is your primary concern, the older suites still have the advantage. That said, you can also bolt Rspamd onto Stalwart manually if you really want — it just defeats the "single binary" appeal.

Webmail and groupware

This is the next big differentiator and the one most people overlook until they need it.

• Mailcow ships with SOGo, which gives you full webmail, calendar (CalDAV), contacts (CardDAV), and ActiveSync for mobile devices. ActiveSync is the killer feature — it's what makes mobile mail "just work" on iPhones and Androids without configuring three separate accounts.
• Mailu ships with Roundcube. Roundcube is a solid IMAP webmail client but has no calendar or contacts integration by default. You're on your own for CalDAV (Radicale is the usual add-on).
• Stalwart ships with a built-in admin UI but no end-user webmail in the core release. They're working on a JMAP-based webmail (codenamed Bulwark / their official webmail project) but as of May 2026 it's still beta. Most people pair Stalwart with an external webmail like Snappymail or use Thunderbird/Mail.app directly via JMAP.

If your users live in a webmail tab all day, Mailcow's SOGo is genuinely the best out-of-the-box experience. For one of my clients I tried to replace SOGo with Roundcube + Radicale + a third-party ActiveSync gateway and gave up after two weekends. Mailcow just works for that use case.

Setup and config — the honest experience

Installing Mailcow

Mailcow's install is genuinely the simplest. Clone the repo, run the generate-config script, edit one file (mailcow.conf), and bring up the stack with docker compose up -d. The first boot takes a few minutes while it pulls images, but everything's running by the end.

The pain points: the docker-compose file is huge, debugging which container is misbehaving requires docker logs across 15 containers, and updates are sometimes opinionated about config changes. The "Moorch 2026" update broke SOGo mail creation for some users — there are GitHub issues still open about it as of early May.

Installing Mailu

Mailu has a web-based setup wizard at setup.mailu.io where you fill out a form (domain, hostname, RAM availability, what features you want) and it generates the docker-compose.yml plus a .env file. You scp those to your server, run docker compose up, and you're 80% there.

The remaining 20% is DNS — SPF, DKIM, DMARC, MX, rDNS — which is universal across all three stacks. Mailu's admin UI is genuinely friendly. For non-technical users who need to add a mailbox or alias, you can hand them the URL and they'll figure it out.

Installing Stalwart

Stalwart is a different shape. You either install via the official install script (which downloads the binary and writes a systemd unit) or run the container. First boot drops you into a setup wizard at the admin URL where you create the master account, configure your domain, set TLS, and pick your storage backend (RocksDB, SQLite, PostgreSQL, MySQL, or FoundationDB).

After that, you're editing the TOML config directly. There's no friendly admin UI for advanced things like Sieve scripts or DKIM key rotation — you do it through the TOML and reload. For me, this is a feature, not a bug. Config in version control, no clicking around. But if you've never written a TOML file, expect a learning curve.

Updates and ongoing maintenance

This is the part nobody talks about until two years in.

Mailcow: Update via ./update.sh, which pulls new images and recreates containers. Usually painless, occasionally requires manual intervention (config schema changes). Update cadence is roughly monthly.

Mailu: Pin a version tag in your docker-compose.yml, edit it to a new version, run docker compose pull && docker compose up -d. Migrations between major versions sometimes need manual database tweaks. Releases roughly every 2-3 months.

Stalwart: Replace the binary, restart the systemd service. That's it. The config schema has been stable since v0.10. I had a v0.9 → v0.11 jump migrate cleanly without intervention. Releases come every few weeks but most are non-breaking.

For me, Stalwart's update story is the single biggest reason I've moved my newer client mail boxes to it. I'd rather copy a binary than debug a Docker network issue at 11 PM.

Deliverability — they're all roughly equal

One myth worth killing: deliverability is not really a function of which mail server you pick. It's a function of:

1. Your IP's reputation (don't pick a VPS provider whose ranges are on Spamhaus blocklists — looking at you, Contabo's older blocks)
2. Your DNS — SPF, DKIM, DMARC, valid rDNS pointing to your hostname
3. Your sending volume and pattern (sudden bursts trigger throttling)
4. Your TLS configuration (modern ciphers, valid cert)

I tested all three with mail-tester.com and they all hit 10/10 with proper DNS setup. Hetzner Cloud and Hostinger Cloud Compute IPs both had clean reputation in my tests. The biggest risk to your deliverability isn't the software — it's accidentally landing on an IP that someone used for spam in 2022.

Real-world: which one I'm actually running where

Across the projects I currently maintain:

• Three of my 7 aggregator sites use Stalwart for inbound contact form mail. Cheap, single binary, basically zero maintenance. I haven't touched the install since I set it up in February 2026.
• One client (logistics helpdesk) runs Mailcow because they need ActiveSync mobile mail and a SOGo webmail their staff already learned.
• One client (Smart POS deployment for ~15 retail outlets) runs Mailu because they wanted Rspamd's stronger spam filtering on a $4/month VPS budget and didn't need calendar/contacts.

So none of them is universally "best" — the answer depends on what your users need to do with the mail.

Common pitfalls I've hit (so you don't have to)

1. Not setting rDNS first. Almost every VPS provider lets you set a PTR record on your IP — do it before you send a single message, otherwise you'll be greylisted everywhere.
2. Trusting the default DKIM key bit length. Mailcow used to default to 2048-bit DKIM, which is fine, but some DNS providers truncate the TXT record at 255 chars and the key arrives broken. Always verify with dig TXT.
3. Letting ClamAV run on a 2 GB box. Mailcow's ClamAV will OOM-kill your VPS. If you're under 6 GB RAM, set SKIP_CLAMD=y immediately.
4. Skipping backups. All three stacks store data locally. I use restic with a Backblaze B2 bucket for nightly snapshots — the entire mail spool plus config is usually under 5 GB for small deployments.
5. Forgetting port 25 might be blocked. Many VPS providers block outbound port 25 by default. Hostinger requires a support ticket to open it. Hetzner requires sending a request. Check this before you commit to a provider for mail.

FAQ

Can I migrate between these stacks later?

Yes, but it's not trivial. Mailbox data moves cleanly via IMAP-to-IMAP sync (use imapsync). Server-side filters, sieve rules, DKIM keys, and admin config don't migrate automatically — you rebuild that from scratch. Plan for a weekend if you're moving a real production setup.

What about Mail-in-a-Box or docker-mailserver?

Both are valid. Mail-in-a-Box is excellent for absolute beginners but is opinionated about everything (Ubuntu only, specific server layout). docker-mailserver is more à la carte than Mailu — bring your own webmail and admin UI. For most readers I think Mailcow/Mailu/Stalwart cover the realistic choices.

Should I just use a relay like Postmark or AWS SES?

If you only need to send mail (not receive), yes — a transactional relay is almost always better than self-hosting. The pain of self-hosted mail is in receiving and the spam fight. If you only need outbound, use a relay and skip this whole article.

Is JMAP worth caring about?

JMAP is genuinely better than IMAP for mobile clients — it batches requests, supports push without idle connections, and uses HTTP transport (so it works through corporate proxies). If you're an early adopter, Stalwart is the only one of these three with first-class JMAP support today. For most users it's not yet a deciding factor since mainstream mail clients are still IMAP-first in 2026.

What if I don't want to run any of these myself?

Migadu, Purelymail, and Fastmail are good managed alternatives starting around $20-30/year for personal use. Self-hosting only makes sense if you have specific privacy or cost reasons or you genuinely enjoy the operations work.

Bottom line

For a new self-hosted email project in May 2026, I'd start with Stalwart unless you specifically need ActiveSync (then Mailcow) or you want Rspamd-grade spam filtering on a 4 GB VPS (then Mailu). The Rust-based future of email tooling is real, and Stalwart is the most credible attempt I've seen to modernize the stack.

Whatever you pick, the hard part isn't the install — it's the DNS, the rDNS, the deliverability tuning, and accepting that you're now responsible for keeping mail flowing 24/7. Plan for backups, monitoring (I use Uptime Kuma for that), and a sensible upgrade cadence. The software is the easy bit.