head to head · open source
Billion Mail vs OpenOutreach
Billion Mail has 15,619 GitHub stars, 1,704 forks, 236 open issues and last shipped 3 months ago. OpenOutreach has 3,041 stars, 560 forks, 1 open issues and last shipped 14 days ago. Billion Mail leads on adoption by 414% (15,619 vs 3,041 stars). Billion Mail is written in Go under AGPL-3.0; OpenOutreach is written in Python under GPL-3.0. Billion Mail has attracted 11% as many forks as stars, OpenOutreach 18%. OpenOutreach was the more recently maintained of the two, and both are self-hostable with no licence fee.
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
| Billion Mail | OpenOutreach | |
|---|---|---|
| GitHub stars | ★ 16K | ★ 3.0K |
| License | AGPL-3.0 | GPL-3.0 |
| Written in | Go | Python |
| Last push | 2026-06-11 | 2026-09-07 |
| Forks | ⑂ 1.7K | ⑂ 560 |
| Self-hosting | Yes | Yes |
| Data ownership | Your server | Your server |
pick Billion Mail if
- You weight community size — 16K stars and counting
- You want the AGPL-3.0 license terms
- Your stack matches Go
- You value the larger contributor base for long-term maintenance
pick OpenOutreach if
- You want the OpenOutreach feature set and don't need the biggest community
- You prefer the GPL-3.0 license terms
- Your stack matches Python
- You evaluated both and OpenOutreach fits your workflow better
About Billion Mail
BillionMail is an open source mail server and email marketing platform written in Go and released under the AGPL 3.0 license. It lives in the self hosted email ecosystem and is described as a solution for newsletters, promotional emails, and transactional messages. The project combines mail server topics such as Postfix, Dovecot, Rspamd, and SMTP with campaign features such as customer management, analytics, templates, and sending control.
read the full Billion Mail overview →
About OpenOutreach
OpenOutreach is an open source AI agent for B2B lead generation, written in Python and licensed under GPL 3.0. It is a self hosted CLI that lets a user describe a product and target market, then finds matching people from a licensed data provider and judges each one against an ideal customer profile learned from those descriptions.
read the full OpenOutreach overview →
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Frequently asked questions
Is Billion Mail or OpenOutreach more popular?
Billion Mail has 15,619 GitHub stars and OpenOutreach has 3,041. Billion Mail has the larger community by that measure.
Are Billion Mail and OpenOutreach free?
Both are open source. Billion Mail is licensed under AGPL-3.0 and OpenOutreach under GPL-3.0. Neither carries a licence fee.
What is the difference between Billion Mail and OpenOutreach?
Billion Mail is written in Go and OpenOutreach in Python. The practical differences are community size, licence terms, language stack and release cadence — all compared in the table above.
Which should I choose, Billion Mail or OpenOutreach?
Choose Billion Mail if you want the larger community (15,619 stars) or its AGPL-3.0 licence terms. Choose OpenOutreach if its feature set, stack or GPL-3.0 licence fits better. Both are self-hostable.