head to head · open source
BillionMail vs OpenOutreach
BillionMail has 15,619 GitHub stars, 1,704 forks, 239 open issues and last shipped 3 months ago. OpenOutreach has 3,041 stars, 560 forks, 1 open issues and last shipped 14 days ago. BillionMail leads on adoption by 414% (15,619 vs 3,041 stars). BillionMail is written in Go under AGPL-3.0; OpenOutreach is written in Python under GPL-3.0. BillionMail 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
| BillionMail | 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 BillionMail 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 BillionMail
BillionMail is an open source mail server, newsletter, and email marketing platform that runs entirely on infrastructure the operator controls. It is written in Go and released under the AGPL 3.0 license, and it lives in the self hosted email and marketing ecosystem alongside the mail transfer and delivery components it bundles, including Postfix, Dovecot, and Rspamd. The project ships as a complete stack rather than a single binary, combining a sending server, a campaign manager, and a webmail client so that one deployment covers transactional mail, promotional campaigns, and newsletters.
read the full BillionMail 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 BillionMail or OpenOutreach more popular?
BillionMail has 15,619 GitHub stars and OpenOutreach has 3,041. BillionMail has the larger community by that measure.
Are BillionMail and OpenOutreach free?
Both are open source. BillionMail is licensed under AGPL-3.0 and OpenOutreach under GPL-3.0. Neither carries a licence fee.
What is the difference between BillionMail and OpenOutreach?
BillionMail 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, BillionMail or OpenOutreach?
Choose BillionMail 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.