Replace / Proton Mail
Best free Proton Mail alternatives (open source, self-hosted) 2026
The best open-source alternative to Proton Mail is Mailcow (or Stalwart) with Mail-in-a-Box, self-hosted on Railway. Mail you run, plus a client you already know. Mailcow is GPL-3.0; Stalwart core is AGPL-3.0 — Outlook, Superhuman, Proton Mail, Fastmail, and HEY without the hosted mailbox seat.
Estimated save $1,200 a year.
Open the stackStart on Railway
How Proton Mail compares
| Proton Mail | Mailcow / Stalwart | |
|---|---|---|
| Pricing model | Hosted subscription | Open-source or fair-code license; you pay the host |
| Hosting | Vendor cloud | Self-hosted on Railway or any VPS |
| Rough monthly cost | Public list price not verified this run | Hosting only — no SaaS seat meter in this repo |
- Mailcow
GPL-3.0 dockerized mail server — the published Outlook path
- Stalwart
AGPL-3.0 core IMAP/JMAP/SMTP (skip SELv2)
- Mail-in-a-Box
CC0-1.0 one-box installer if you want that path
FAQ
- What is the best free open-source Proton Mail alternative?
- The best open-source alternative to Proton Mail is Mailcow (or Stalwart) with Mail-in-a-Box, self-hosted on Railway. Mail you run, plus a client you already know. Mailcow is GPL-3.0; Stalwart core is AGPL-3.0 — Outlook, Superhuman, Proton Mail, Fastmail, and HEY without the hosted mailbox seat.
- Is it free?
- The Mailcow / Stalwart licenses are open source or fair-code. You still pay hosting (Railway or any VPS) and any APIs the stack calls. There is no Proton Mail seat or task bill on this path.
- Can I migrate from Proton Mail?
- Yes. Start with the workflows or data you actually use, then cut over. The Mailcow / Stalwart stack page has the agent prompt and the cost table; most teams rebuild the slice that matters and leave old Proton Mail links until they expire.
- How do I deploy it?
- Open the Mailcow / Stalwart stack, copy the agent prompt, and deploy on Railway (one service, PORT, and a volume when the app needs disk). Mail wants a public IP, MX, and ports 25/465/587 — a VPS more than a single Railway service. Mailcow is docker-compose. Stalwart is one binary plus a volume. Mail-in-a-Box expects to own the box. Thunderbird stays on the laptop. No one-click template in this repo yet — Start on Railway only if you already know the MX story. Gmail-shaped Workers mail stays on /stacks/stalwart-mail.
- What does this replace?
- Microsoft Outlook / Superhuman / Proton Mail / Fastmail / HEY. The published small-team estimate on this stack is $1,200 a year.
Related pages
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