listmonk is a self-hosted, open-source platform designed for high-performance email marketing. It allows you to manage millions of subscribers across multiple lists while maintaining full control over your data.

The tool features a multi-threaded email queue that supports high-throughput delivery via multiple SMTP servers. You can set granular rate limits to ensure your sending reputation remains intact across different providers.

Marketers can use SQL expressions to query and segment their audience with precision. This allows for highly targeted campaigns based on specific subscriber data stored in your Postgres database.

Creating content is flexible with support for Markdown, a drag-and-drop builder, or raw HTML. You can also use dynamic templates with over 100 functions to personalize subject lines and body text.

Beyond standard newsletters, the system handles transactional emails and webhooks. This enables you to send automated messages via email, SMS, or WhatsApp through a single API.

The application is resource-efficient, using minimal RAM even when processing millions of emails. This makes it a cost-effective choice for creators who want to avoid expensive per-subscriber pricing.