Open-Source Alternatives to Proton Mail

Mailu is a complete email distribution system deployed as a suite of containerized images. It provides a self-hosted email infrastructure that integrates a webmail client interface with a centralized administration dashboard for managing domains, user accounts, and storage quotas. The system focuses on email deliverability and security through a framework that implements identity verification records and digital certificates. This includes the use of identity signatures and encryption to secure mail transport and prevent domain spoofing. The platform includes layered spam and malware filteri

Mail-in-a-Box is a self-hosted email server appliance that automates the deployment of SMTP, IMAP, and POP3 services on Linux. It functions as a complete suite including a DNS management server, a spam and abuse filter, and a web-based administrative control panel for managing users, aliases, and storage quotas. The project distinguishes itself through a high degree of automation for email security and authenticity. It automatically provisions and maintains SPF, DKIM, DMARC, and DNSSEC records to prevent domain spoofing, while managing the installation and rotation of TLS certificates and enf

Mox is a self-hosted email server that runs as a single compiled Go binary, handling the full lifecycle of sending and receiving email through SMTP, IMAP4rev2, and a built-in webmail application. It is designed to be operated without external dependencies or runtime plugins, with all mail services — including spam filtering, queue management, and web interfaces for administration and account management — contained in one executable. The server distinguishes itself through automated TLS certificate management via ACME, DNS-based autoconfiguration for email clients, and file-based configuration

Mailcow-dockerized is an open-source email hosting platform that provides a complete, self-hosted infrastructure suite. It bundles message transfer, storage, and security protocols into a modular, containerized environment designed for deployment on private infrastructure. The platform distinguishes itself by integrating a centralized management interface for configuring mail domains and user accounts alongside collaborative tools like shared calendars and contact lists. It includes automated security features such as integrated spam and malware filtering gateways, as well as automated certif

Mailpile is an encrypted email client and high-volume mail indexer that provides a web-based portal for managing electronic mail. It functions as a private email management system designed to protect user privacy and data control. The project features a search engine optimized for indexing and retrieving large volumes of email on consumer hardware. It includes a Bayesian email filter for automated message classification and tagging. The system supports secure communication through the integration of public-key encryption and signing for sending and receiving messages. Additional capabilities

Mail hosting made simple

Opinionated email server

Rainloop Webmail is a self-hosted, browser-based email application that connects to external mail servers using IMAP and SMTP protocols. It operates as a stateless client, fetching data directly from servers without requiring a local database to store messages. The system supports multi-account email management, allowing users to link multiple email identities to a single session for simultaneous access across different browser tabs. It includes a plugin-based extension system and tools for user interface customization and branding. The application provides capabilities for email workflow au

CryptPad is a self-hosted, zero-knowledge office suite designed for real-time collaborative editing and content management. It provides a privacy-centric infrastructure where documents, files, and notes are encrypted in the browser before transmission, ensuring that the server administrator cannot access the underlying data. The platform implements zero-knowledge user authentication, utilizing cryptographic keys to verify identities so that plain text passwords are never stored on the server. To further isolate sensitive operations, the system employs a security architecture that separates th

Linsa.io is an end-to-end encrypted cloud storage service and zero-knowledge data vault. It functions as a private content sharing platform that encrypts files and data on the client side, ensuring only the owner can access the stored content. The project employs a local-first approach, processing data updates and encryption on the local device before syncing encrypted blobs to a remote persistence layer. It uses a zero-knowledge architecture where the service provider cannot access decryption keys or view the plaintext content of stored files. The platform provides capabilities for private

Send is an end-to-end encrypted file sharing service that encrypts files on the sender's device before upload, ensuring the server never sees plaintext content. It generates secure download links that are designed for single use, automatically removing access after the first successful download, and associates each share with a time-limited access token that expires after a set duration. The service operates without requiring user accounts, lowering friction for ephemeral sharing, and uses cryptographic key derivation to generate decryption keys from the download URL, eliminating server-side

Himalaya is a command line email client and a suite of toolsets for email protocol implementation. It provides a terminal-based interface for managing email accounts using IMAP and SMTP protocols. The project includes a PIM framework and specialized libraries for building personal information management applications that integrate emails, contacts, calendars, and tasks. It features a PGP email encryptor for end-to-end encrypted communication and an email data exporter that extracts messages and metadata into JSON format for use in external scripts. The system covers a broad range of email ma