Papercut SMTP – The Simple Desktop Email Server (github.com)

Papercut SMTP, a dual-function tool serving as both a quick email viewer and SMTP server, has been announced to aid developers in testing email functionalities within applications. By pointing applications to localhost:25, developers can catch and view any emails sent during the development process without them being delivered, offering immediate visibility into email content, including bodies, HTML, headers, and attachments. The installation is straightforward, with options available for 64-bit, 32-bit, and ARM64 systems, along with a Docker setup for containerized use. Significantly, Papercut SMTP includes an optional Model Context Protocol (MCP) server that facilitates interaction with AI agents, like Claude Code. This integration allows for the inspection and manipulation of email data sent by applications, enabling tests for correctness and content validation while ensuring a clean slate between test runs. Although the MCP server is disabled by default, its activation opens up opportunities for deeper AI-driven testing and development workflows. As an open-source tool licensed under the Apache License, Papercut SMTP not only streamlines the testing process but also invites community support for ongoing project sustainability.