Email

6 open source tools compared. Sorted by stars — scroll down for our analysis.

Tool	Stars	Velocity	Language	License	Score
Listmonk High-performance, self-hosted newsletter manager	19.3k	+57/wk	Go	GNU Affero General Public License v3.0	71
Nodemailer Send emails with Node.js	17.5k	+13/wk	JavaScript	—	69
Postal Fully featured open source mail delivery platform	16.4k	+12/wk	Ruby	MIT License	79
MailHog SMTP testing tool	15.9k	+22/wk	Go	MIT License	79
Mailtrain Self-hosted newsletter app	5.7k	—	JavaScript	GNU General Public License v3.0	68
Plunk Open source email platform	4.9k	+21/wk	TypeScript	GNU Affero General Public License v3.0	61

Our Analysis

Listmonk19.3k★

Listmonk is the self-hosted newsletter manager that makes Mailchimp feel like a hostage situation. A single Go binary with PostgreSQL, it handles subscriber management, campaign sends, and analytics without charging you per subscriber. Pair it with any SMTP relay — Amazon SES at $0.10/1000 emails — and you've got a newsletter stack for pennies. If you're an indie hacker running a newsletter and tired of Mailchimp's pricing tiers, Listmonk is your exit. It's fast, minimal, and just works. Mailtrain (Node.js) offers more automation and WYSIWYG templates but feels abandoned. Plunk is the newer open-source option with marketing workflows. Buttondown is the paid indie-friendly alternative. The catch: Listmonk is AGPL-3.0, so your modifications must be open-sourced. There's no built-in automation — no drip sequences, no behavioral triggers. The template editor is basic. And "self-hosted email" means you own deliverability too: SPF, DKIM, warm-up, reputation management. That's real work most people underestimate.

Nodemailer17.5k★

Nodemailer is the boring, reliable way to send email from Node.js — and boring is exactly what you want from email infrastructure. It connects to any SMTP server, handles attachments, HTML templates, and edge cases that have existed since email was invented. Fifteen years of battle-testing means the weird Outlook rendering bugs are already solved. If you have your own SMTP credentials and just need to send email, Nodemailer does the job. Resend is the modern API-based alternative with beautiful React Email templates — but it's a paid service. SendGrid and Mailgun are the enterprise options. EmailJS is lighter but less capable. The catch: Nodemailer is SMTP-only in a world moving to API-based email services. You're managing SMTP connections, handling retries yourself, and debugging delivery issues at the protocol level. For transactional email at scale, an API service like Resend or SES is less painful. And Nodemailer's license (MIT-adjacent but custom) has caused occasional confusion — check the terms.

Postal16.4k★

Self-hosted Mailgun, and it actually works. Postal handles transactional email delivery at scale — SMTP, webhooks, tracking, bounce management, multi-domain — all running on your own infrastructure. If you're sending thousands of emails and Mailgun's per-message pricing is eating your margins, Postal flips the economics. Mailtrain is the open source newsletter alternative but focuses on marketing, not transactional. Haraka is a raw SMTP server without the management UI. Sendgrid and Postmark are the polished commercial options, but you're paying per email forever. Postal gives you click tracking, open tracking, delivery monitoring, and a comprehensive API. It handles incoming mail too, which most alternatives skip. One instance can manage multiple organizations and domains. The catch: running your own mail server is an ops commitment. IP reputation, SPF/DKIM/DMARC setup, deliverability monitoring — Postal gives you the platform, not the expertise. If you don't understand email deliverability, your carefully crafted emails will land in spam. Also, scaling to millions of emails means serious infrastructure planning.

MailHog15.9k★

The OG email testing tool that every tutorial still recommends — but hasn't been updated since 2020. MailHog captures SMTP traffic in development so you can inspect emails without actually sending them. Simple concept, simple tool, and it worked great for years. The problem: it's abandoned. Mailpit is the direct drop-in replacement — same ports, compatible API, actively maintained, with full-text search and email tagging. MailCrab is a modern Rust-based alternative with a slick UI. For SaaS teams, Mailtrap offers a hosted version with a production path. If you're starting a new project, skip MailHog entirely and use Mailpit. If you have MailHog in an existing docker-compose, Mailpit uses the same default ports (1025/8025) so migration is literally swapping the image name. The catch: MailHog itself is dead software walking. 15K+ stars on GitHub give it false credibility — those stars are historical, not a signal of health. No security patches, no bug fixes, no new features. Using unmaintained software in your dev pipeline is a quiet risk you don't need to take.

Mailtrain5.7k★

Mailtrain is the self-hosted Mailchimp alternative that tried to do everything — multi-user support, automation workflows, WYSIWYG templates, advanced segmentation, and detailed deliverability analytics. Built on Node.js and MySQL, it's the most feature-rich open-source email marketing tool if you need structured campaigns with multiple collaborators. If you need automation workflows, A/B testing, and multi-user collaboration in a self-hosted newsletter platform, Mailtrain has more built-in features than Listmonk. Listmonk is faster, lighter, and easier to deploy but lacks automation. Plunk is the newer alternative with marketing plus transactional in one. Mautic is the open-source marketing automation suite if you need even more. The catch: Mailtrain is labeled "beta-grade software" by its own developers. The project's maintenance cadence is slow — version 2 was a complete rewrite that broke backward compatibility, and updates are infrequent. Setup is complex compared to Listmonk's single binary. For most indie hackers, Listmonk's simplicity and active development make it the safer bet.

Plunk4.9k★

Plunk is the open-source email platform that does what Resend won't — transactional and marketing emails in one tool. Built on AWS SES, it handles campaign broadcasts, workflow automation, and triggered emails alongside your transactional sends. Self-host it and pay $0.001 per email through SES instead of per-subscriber pricing. If you're an indie hacker sending both product emails and marketing campaigns, Plunk consolidates two tools into one. Resend has a better developer experience and React Email templates but only does transactional. Listmonk is the lightweight newsletter alternative without transactional support. SendGrid does both but at enterprise pricing. The catch: Plunk is AGPL-3.0 — your modifications must be open-sourced if you distribute them. The project is younger and less battle-tested than Listmonk or Nodemailer. The documentation is thinner. And building on AWS SES means you inherit SES's deliverability management — sandbox mode, domain verification, reputation monitoring are all your responsibility.