Mailpile is a modern, fast web-mail client with user-friendly encryption and privacy features. The development of Mailpile is funded by a large community of backers and all code related to the project is and will be released under an OSI approved Free Software license.

Mailpile places great emphasis on providing a clean, elegant user interface and pleasant user experience. In particular, Mailpile aims to make it easy and convenient to receive and send PGP encrypted or signed e-mail.

Mailpile's primary user interface is web-based, but it also has a basic command-line interface and an API for developers. Using web technology for the interface allows Mailpile to function both as a local desktop application (accessed by visiting localhost in the browser) or a remote web-mail on a personal server or VPS.

The core of Mailpile is a fast search engine, custom written to deal with large volumes of e-mail on consumer hardware. The search engine allows e-mail to be organized using tags (similar to Gmail's labels) and the application can be configured to automatically tag incoming mail either based on static rules or bayesian classifiers.