Listmonk

Listmonk is a self-hosted newsletter and mailing list manager, the open source answer to Mailchimp. It's a single Go binary backed by Postgres that handles subscriber management, campaign creation, analytics, and sending, all through a clean web UI. Connect it to any SMTP service (Amazon SES, Postmark, your own server) and you're running your own Mailchimp for the cost of a VPS.

What makes Listmonk stand out: performance. It can handle hundreds of thousands of subscribers without breaking a sweat. The templating system is flexible, transactional emails work alongside campaigns, and the API is well-documented for programmatic access. Subscriber segmentation, A/B testing, bounce handling, it's all there.

Deployment is dead simple compared to alternatives. Docker Compose up, point it at a Postgres database, configure SMTP, done. The whole thing runs on a $10/mo VPS comfortably for 50K+ subscribers.

The catch: no drag-and-drop email builder. You write HTML templates or use the built-in markdown editor. If your marketing team expects a visual builder like Mailchimp's, they'll be disappointed. There's no built-in landing page builder or signup form designer either; you build those yourself or use the embed code. And the community, while growing, is smaller than commercial ESPs; you're on your own for advanced deliverability tuning.