head to head · open source
Inbox Zero vs Hyvor Relay
Inbox Zero has 12,238 GitHub stars, 1,536 forks, 209 open issues and last shipped yesterday. Hyvor Relay has 897 stars, 63 forks, 56 open issues and last shipped yesterday. Inbox Zero leads on adoption by 1,264% (12,238 vs 897 stars). Inbox Zero is written in TypeScript under a custom or non-standard licence; Hyvor Relay is written in PHP under AGPL-3.0. Inbox Zero has attracted 13% as many forks as stars, Hyvor Relay 7%. Inbox Zero was the more recently maintained of the two, and both are self-hostable with no licence fee. The two share 1 topic tag (email), so they are genuine substitutes rather than adjacent tools.
Two open source projects, one decision. Both are free and self-hostable — the differences are community size, license terms, language stack and release pace.
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Side by side
| Inbox Zero | Hyvor Relay | |
|---|---|---|
| GitHub stars | ★ 12K | ★ 897 |
| License | Custom / other | AGPL-3.0 |
| Written in | TypeScript | PHP |
| Last push | 2026-09-17 | 2026-09-17 |
| Forks | ⑂ 1.5K | ⑂ 63 |
| Self-hosting | Yes | Yes |
| Data ownership | Your server | Your server |
pick Inbox Zero if
- You weight community size — 12K stars and counting
- You want the Custom / other license terms
- Your stack matches TypeScript
- You value the larger contributor base for long-term maintenance
pick Hyvor Relay if
- You want the Hyvor Relay feature set and don't need the biggest community
- You prefer the AGPL-3.0 license terms
- Your stack matches PHP
- You evaluated both and Hyvor Relay fits your workflow better
About Inbox Zero
Inbox Zero is an open source AI email assistant written in TypeScript and placed in the email productivity ecosystem. It is a web application built with Next.js, shadcn/ui, Prisma, and related tools. The project describes itself as a 24/7 assistant that organizes email, drafts replies, manages calendar context, and handles attachments.
read the full Inbox Zero overview →
About Hyvor Relay
Hyvor Relay is an open source email API aimed at developers, written primarily in PHP with Symfony for the API backend and Go for the email workers, webhook handlers, DNS server, and incoming SMTP server. The frontend is built with SvelteKit and the Hyvor Design System, and PostgreSQL serves both as the database and as the queue. It lives in the PHP and Go ecosystems, is licensed under AGPL 3.0, and is positioned as a cloud and self hosted alternative to SES, Mailgun, and SendGrid.
read the full Hyvor Relay overview →
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Frequently asked questions
Is Inbox Zero or Hyvor Relay more popular?
Inbox Zero has 12,238 GitHub stars and Hyvor Relay has 897. Inbox Zero has the larger community by that measure.
Are Inbox Zero and Hyvor Relay free?
Both are open source. Inbox Zero has no licence declared in this registry, and Hyvor Relay is licensed under AGPL-3.0. Both are free to self-host.
What is the difference between Inbox Zero and Hyvor Relay?
Inbox Zero is written in TypeScript and Hyvor Relay in PHP. The practical differences are community size, licence terms, language stack and release cadence — all compared in the table above.
Which should I choose, Inbox Zero or Hyvor Relay?
Choose Inbox Zero if you want the larger community (12,238 stars) or its Custom / other licence terms. Choose Hyvor Relay if its feature set, stack or AGPL-3.0 licence fits better. Both are self-hostable.