chasquid is a production-grade SMTP (email) server written in Go, focusing on simplicity, security, and ease of operation. It handles incoming and outgoing email with full support for modern email security standards including STARTTLS, DKIM signing and verification, SPF checking, MTA-STS enforcement, and per-domain security level tracking. The server architecture is modular: the main daemon delegates SMTP protocol handling to the internal/smtpsrv package, manages a persistent email queue via internal/queue, performs alias resolution with hooks via internal/aliases, and delivers mail either locally through an LMTP-based MDA (cmd/mda-lmtp) or remotely via SMTP courier with TLS and MX fallback. Authentication integrates with Dovecot or a local user database using scrypt password hashing. Configuration is defined via protobuf text format, supporting hot reload of domains, users, and aliases without restart. The repository includes CLI tools for administration (chasquid-util), SMTP connectivity checking (smtp-check), and Dovecot authentication testing (dovecot-auth-cli). A comprehensive test suite covers unit, integration, and fuzz tests, with test data for DKIM, SPF, aliases, and various protocol edge cases. The repository also provides a Dockerfile for containerized deployment and extensive documentation in Markdown and man pages. While primarily an application, the codebase contains several well-designed internal packages that could be extracted for reuse, such as the network tracing library, safe I/O utilities, and OpenMetrics exporter.
Nette Mail is a standalone PHP library for creating and sending emails with support for SMTP, sendmail, DKIM signing, and fallback mechanisms. It provides a clean API for composing emails with HTML/text bodies, attachments, embedded images, and automatic text alternative generation. The architecture follows a modular design with separate concerns for message creation (Message/MimePart), sending (multiple Mailer implementations), signing (DkimSigner), and HTML processing (HtmlComposer, CssInliner). The library is framework-agnostic but integrates well with Nette DI and Tracy debugging tools.
Matcha is a full-featured terminal email client (TUI) written in Go, using the Bubble Tea framework. It supports multiple email protocols (IMAP, JMAP, POP3, Maildir) and provides a rich set of features including PGP/SMIME encryption, OAuth2 authentication, a Lua plugin system with 35+ community plugins, background daemon for push notifications and sync, spellcheck, i18n with 11 languages, and a configurable theme system. The architecture is modular: a backend provider interface abstracts protocol implementations, a daemon runs as a background process communicating via JSON-RPC over Unix sockets, and the TUI is built with composable Bubble Tea models. The codebase demonstrates strong engineering practices with extensive test coverage, CI/CD pipelines, cross-platform packaging (Homebrew, Snap, Flatpak, Nix, WinGet), and a well-designed plugin API. It is not a data research project; it is a production-grade application.
WePush is a Java application monorepo with two coexisting generations of a multi-channel bulk messaging system. The legacy `src/main` tree is a Swing desktop client that manages accounts, message templates, recipient lists, tasks, and run history, and sends via WeChat (official accounts, mini programs, WeCom), SMS vendors, email, HTTP, DingTalk/Feishu bots, and carrier SMS protocols (CMPP/SMGP/SGIP/SMPP). It persists to SQLite through MyBatis and generates UI with IntelliJ GUI Designer forms. The `next/` tree is a modular, distributed push orchestration platform: a Spring Boot control plane (REST + gRPC), remote agents connected via an mTLS gRPC stream, a provider SPI with built-in HTTP, Aliyun SMS, SMTP, WeChat, and bot providers, and pluggable signed PF4J plugins for carrier protocols. It adds multi-tenant workspaces, secret envelope encryption, artifact storage (local/S3), audience streaming import, run state machines with idempotency and retry, schedule management, a React/Vite web UI, an Electron desktop shell, and a Java SDK. Persistence is SQLite for standalone mode or PostgreSQL for server mode, with Flyway migrations and JDBC repositories. The Next codebase is well-architected with core-api/engine/provider-spi/service/domain/infrastructure separation, ADRs, architecture tests, integration tests, CI, and installers. However, the repository as a whole carries the legacy desktop codebase in parallel, duplicating several domain concepts and retaining generated UI code and older dependencies. This split and the aging legacy portions are the main sources of technical debt.
DockYard/elixir-mail is an Elixir library for building, parsing, and rendering email messages according to RFC 2822 and related MIME standards. It provides a composable API to create simple and multipart email messages, handle various transfer encodings (Base64, Quoted-Printable, 7bit, 8bit, binary), and parse incoming email into structured data. The library is structured around a core `Mail.Message` struct with separate modules for encoding, parsing, rendering, and MIME type lookup. It does not require any external runtime dependencies beyond the Erlang/OTP standard library.
This is a PHP library for parsing MIME email messages conforming to RFC 822/2822/5322. It wraps the `mailparse` PECL extension to provide a clean, object-oriented API for extracting headers, plain text and HTML bodies, attachments, and embedded content from raw email data (file, string, or stream). The library features a middleware system for custom MIME part processing, configurable attachment filename conflict strategies (suffix, random, throw), charset decoding with an extensive alias map, and type-safe enums for body type and filename strategy. It is designed for use in webmail clients, email processing pipelines, and Postfix integration, with support for complex MIME structures including multipart/alternative, inline images, and nested RFC822 messages. The test suite includes over 30 real-world email fixtures covering edge cases, making the library robust enough for production use.
Mail-Archiver is a production-grade ASP.NET Core 10 web application for archiving emails from IMAP, Microsoft 365 (Graph), and local imports (MBOX, EML). It provides a full MVC UI for searching, viewing, exporting, restoring, and managing archived emails, alongside a read-only REST API (v1) and a Model Context Protocol (MCP) server for AI agent integration. The system features background job processing for sync, batch operations, deduplication, retention policies, and audit exports, all backed by PostgreSQL with full-text search. Authentication supports local password (PBKDF2), OpenID Connect, and API keys, with two-factor authentication and role-based access control. The codebase is well-structured with clear separation of concerns: provider-specific services (IMAP, Graph, Mbox), shared utilities, and a core service layer. Extensive unit and integration tests (xUnit) cover critical paths, and Docker Compose provides a reproducible test environment. While some technical debt exists (raw SQL in core services, in-memory job tracking, German comments in places), the overall architecture is solid and the reusable components (static helpers, deduplication strategies, background job patterns) demonstrate high craftsmanship.
TrendRadar is a configurable news aggregation and trend analysis system that crawls hot lists from 11+ Chinese platforms (Zhihu, Weibo, Douyin, Bilibili, etc.) and RSS/Atom feeds, filters content via keyword DSL or AI-based interest matching, performs AI-powered analysis (sentiment, controversy, topic trends), generates rich HTML reports, and pushes notifications to 9+ channels (Feishu, DingTalk, Telegram, Email, ntfy, Bark, Slack, WeCom, generic webhook). It is primarily an application (with CLI entry points, scheduling via timeline.yaml, Docker/GitHub Actions deployment) but incorporates data-pipeline patterns such as multi-stage ETL (crawl → store → filter → analyze → report), SQLite storage with optional S3 remote sync, and AI batch processing. The architecture is a modular monolith: the core `trendradar` package handles all orchestration, while a separate `mcp_server` package exposes 20+ tools via Model Context Protocol (MCP) for LLM integration. The system is heavily config-driven (YAML and text files) and includes a standalone web-based config editor. External dependencies include the third-party newsnow API (for hot lists), LiteLLM (for AI model abstraction), and various notification service APIs. The codebase demonstrates good craftsmanship with clean abstractions (storage backends, notification dispatcher, AI client), though some duplication exists between the core and MCP notification logic, and the extensive configuration surface requires careful maintenance.