Schleuder

Schleuder is an email list manager built specifically for groups that require encrypted communication. Subscribers can send encrypted messages to the list, which Schleuder decrypts, re-encrypts individually for each subscriber, and distributes. It uses GPG for all cryptographic operations and maintains a shared keyring for the list. This means no single subscriber can read a message intended for the list unless they are a member. Schleuder runs on Linux and requires no external database. It integrates with common mail transport agents like Postfix or Exim via aliases. The software is written in Ruby, uses the GPGME library, and supports key management commands sent via email.

Schleuder is free software released under the GNU GPLv3 or later. It is maintained by the Free Software Foundation Europe (FSFE) as part of their infrastructure projects. Originally developed for internal FSFE team communication, it is now available for any organization that needs to discuss sensitive topics via email without exposing plaintext to a central server operator. The project provides detailed setup documentation and a small but active community for support.