Open-Source Email Marketing: What’s Actually Maintained in 2026

A lot of pages on the open web claim to compare “open-source email marketing software” and quietly include projects that are commercial, abandoned, or just self-hosted-but-proprietary. The categories matter — they imply different rights, different long-term risks, and different operational realities. This page is the disambiguation we’ve wanted to link to for a while.

The three categories people conflate

1. Open source

A licence approved by the Open Source Initiative — typically AGPL, GPL, MIT, Apache 2.0, or BSD. You can read the source, run it for any purpose, modify it, and redistribute modifications under the same licence. The OSI Definition is the standard most people use when they say “open source” in a strict sense.

For email marketing platforms specifically, AGPL is the common choice (Listmonk, Mautic, phpList, Keila). AGPL has a “network use is distribution” clause that requires source disclosure even if you’re only running the software as a service — important if you’re a SaaS vendor wanting to use one of these as a backend.

2. Source-available

You can read the source code but the licence imposes restrictions that the OSI doesn’t accept as open source. Common examples in adjacent industries: Business Source Licence (BSL), Server Side Public Licence (SSPL), Elastic Licence v2.

In email marketing this category is rare so far — most non-OSS options are flatly commercial closed-source. The category matters because it sometimes gets marketed as “open” and is not, and because the legal terms vary significantly.

3. Proprietary self-hosted

Closed-source software you license commercially but run on your own infrastructure. You don’t get the source. You get a licence to install and run, usually with version-update and support entitlements tied to the licence.

Examples in this category: Sendy, Broadcast. Calling either of these “open source” is wrong; calling them “self-hosted” is correct.

Why this matters more than the checkbox

If your reason for wanting “open source email marketing” is one of the genuine reasons below, the right category may not be open source.

Most people asking for “open-source email marketing” actually want the first two rows and are surprised when they realise self-hosted proprietary satisfies them just as well. The licence is one variable; what matters is the use case.

What’s actually maintained in 2026

We checked each of these against the maintenance criteria below as of May 2026: public commits in the last 6 months, a release in the last 12 months, and active issue triage. Specifics drift; sense-check before committing to one.

Open-source platforms that pass

• Listmonk (AGPL, Go) — Active. Steady release cadence, responsive maintainer.
• Mautic (GPL, PHP) — Active under a community foundation. Sponsored by multiple agencies. Major version cadence improved post-Acquia.
• Keila (AGPL, Elixir) — Active, smaller team, EU-based.
• phpList (AGPL, PHP) — Active maintenance, conservative pace.
• Mailtrain (GPL, Node.js) — Active, slower release rhythm.

Open-source projects to be cautious about

• OpenEMM / AGNITAS — Splintered project history; commercial fork dominant. The community OSS edition’s status varies.
• Various WordPress plugin “newsletters” — Many are open-licence-on-paper but in practice work only via a paid add-on. Read the licence and the upgrade pipeline carefully.

Proprietary self-hosted (not open source)

• Sendy — Long-running, maintained, commercial.
• Broadcast — Maintained by us; commercial; self-hosted via Docker.

This is not a “good vs. bad” axis. It is a “what are you actually buying” axis.

The AGPL question for email marketing

If you’re a company that wants to resell email marketing to your customers as part of a SaaS product (white-label), the licence matters specifically.

• AGPL (Listmonk, Mautic, phpList, Keila): Network use triggers the source-disclosure obligation. If you build a SaaS on top, you must make your modifications available to users. Most companies considering this route either accept the obligation, dual-license with the upstream, or pick a non-AGPL option.
• GPL/MIT/Apache (Mailtrain, etc.): Network use doesn’t trigger disclosure. Modifications you don’t redistribute as binaries stay private.
• Proprietary self-hosted (Sendy, Broadcast): Re-bundling requires a separate licence agreement with the vendor.

For most internal use cases — sending your own newsletters from your own server to your own subscribers — none of these obligations bite. The AGPL only becomes load-bearing when you’re hosting it as a service for others.

“Open-source Mailchimp” — what people actually mean

The search phrase “open-source Mailchimp” is one of the most common ways into this topic. Mailchimp itself is not, and has never been, open source. The phrase usually means one of three things:

1. “I want a Mailchimp-shaped product I can self-host.” → Mautic and Broadcast are closest in scope.
2. “I want a newsletter tool I can self-host, simpler than Mailchimp.” → Listmonk or Keila.
3. “I want Mailchimp’s automation graph for free.” → Mautic is the only realistic OSS answer; allocate setup time.

If you’re searching for “self-hosted Mailchimp” the Mailchimp alternative page covers the cost and feature angle in more depth.

When licence is the deciding factor

Three scenarios where it genuinely is:

1. You serve regulated clients whose contracts require source-code escrow. Open source covers the escrow obligation automatically. Source-available or proprietary self-hosted require explicit escrow contracts.
2. You’re a government, public-sector, or research organisation with a policy preference for OSS. Self-explanatory.
3. You expect to fork. If you anticipate needing custom behaviour the vendor won’t ship, OSS is materially safer.

Outside those scenarios, the licence is a preference, not a constraint.

Frequently asked

Is there an open-source alternative to Mailchimp?

Several. Mautic is closest in scope; Listmonk and Keila are closest in modern UX. None of them match Mailchimp’s CRM and ecommerce features — they’re focused email tools.

Is Broadcast open source?

No. Broadcast is commercial proprietary software, self-hosted under a one-time licence. We acknowledge that’s a meaningful difference from the OSS options and we don’t market it as open source.

What’s the difference between AGPL and GPL for email marketing software?

GPL requires source disclosure when you distribute binaries. AGPL requires source disclosure when you make the software available over a network. For a company hosting an email tool as a service for clients, AGPL is the more demanding licence. For a company sending its own newsletters from its own server, the two are functionally equivalent.

Can I use an AGPL platform like Listmonk for client work?

Internal use — yes, no obligation triggers. Hosting it as a service for your client — you must make modifications available to users of the service. Many agencies handle this by contributing upstream and shipping unmodified versions.

Are open-source platforms less secure?

No, and this is one of the few areas where the licence genuinely doesn’t matter. Security depends on the project’s maintenance practices, your patch cadence, and your configuration. There are well-maintained OSS platforms and well-maintained commercial ones; there are abandoned versions of both.

Related

• Self-hosted email marketing software (2026 comparison)
• Self-hosted broadcast email — costs and trade-offs
• The self-hosted Mailchimp alternative
• EU data sovereignty for email marketers in 2026