Senlo is an open-source, self-hosted email infrastructure platform designed for teams seeking an alternative to services such as Postmark and Resend. It combines visual email design with tools for managing triggered messages, while supporting provider-agnostic infrastructure and giving users greater control over their email stack and data.

At its core is a visual editor built around a row, column, and block layout. Users can create responsive emails with a drag-and-drop builder, MJML-powered rendering, custom merge tags for personalization, and a real-time preview. Designs are nondestructive and stored in a predictable JSON format.

Senlo also provides a trigger API for sending transactional messages, including order confirmations, password resets, and notifications from a backend. Trigger logs offer visibility into delivery status, errors, and performance, while analytics track opens, clicks, and bounces through event logs. The platform is available as open-source software under the AGPL-3.0 license, with documentation and GitHub resources for users who want to deploy and manage their own email infrastructure.