Bird Email API
Email sending API & SMTP relay with analytics and deliverability tooling
Open-Source Projects
Discover top open-source software, updated regularly with real-world adoption signals.
Discover top open-source software, updated regularly with real-world adoption signals.
Lightweight SMTP server for high-volume email reception in Go
Go-Guerrilla is an SMTP daemon designed to receive large volumes of email quickly. Features modular backends, hot-reloadable config, and multi-server support with MySQL and Redis integration.
Go-Guerrilla is a lightweight SMTP server written in Go, purpose-built for receiving and processing large volumes of email. Originally developed for GuerrillaMail.com—which handles millions of emails daily—it functions as a Mail Transfer Agent (MTA) focused exclusively on rapid email ingestion without sending capabilities.
The daemon features a modular backend system using chainable "Processors" that handle email parsing, validation, and storage. Out-of-the-box support includes MySQL, Redis, MailDir, and FastCGI processors. The producer-consumer architecture leverages Go's concurrency primitives to maximize throughput on multi-core systems.
Deploy Go-Guerrilla as a standalone daemon via the guerrillad binary or import it as a package into your Go application. Configuration supports hot-reloading, allowing you to add or remove servers, update TLS certificates, and modify settings without restart. Graceful shutdown minimizes email loss during maintenance windows. The software supports both STARTTLS and SMTPS, with resource pooling to reduce garbage collection overhead.
When teams consider Go-Guerrilla, these hosted platforms usually appear on the same shortlist.
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Embedded SMTP Receiver
Import as Go package into SaaS application to handle inbound email without external dependencies
No, it functions exclusively as a receiving MTA. It grabs incoming email, processes it, and disconnects quickly without sending capabilities.
Processors are modular components chained via configuration to handle email tasks. Examples include HeadersParser for parsing, MySQL for storage, and Debugger for logging. You can create custom processors or use vendor-provided ones.
The original repository was abandoned in 2019. Community member Philipp revived it at github.com/phires/go-guerrilla and is actively maintaining the fork.
Yes, Go-Guerrilla supports hot-reloading. You can add/remove servers, update TLS certificates, and change most settings without restarting the daemon.
MySQL and Redis are supported out-of-the-box. Vendor-provided processors include MailDir and FastCGI. You can also implement custom processors for other storage systems.
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