Smtp GitHub Repositories (2026) · Open Source Tools

Emails at the heart of your business logic!

📨 Open-Source Email API for Developers. Cloud & Self-hosted Alternative to SES, Mailgun, SendGrid.

DavMail POP/IMAP/SMTP/CalDAV/CardDAV/LDAP Exchange and Office 365 Gateway - Synced with main subversion repository at

Official master for the Greenmail project

A PHP library for performing email addresses validation via SMTP

Written by humans. WTX is a collection of different transport implementations and related tools focused primarily on web technologies.

A local debug server and utilities set for PHP projects

Aplus Framework Email Library

Email, SMS & phone-call infrastructure for AI agents — send and receive real email and text messages, and place agent-driven outbound voice calls, all programmatically

The open-source email platform — self-host on your own AWS SES, or use the cloud. Resend-compatible API.

Knock-Knock: A Live, Multi-Protocol Honeypot Dashboard of Internet Break-in Attempts - 13 Protocols, an Extensible Framework, and a Threat-Intelligence Database Serving a Public IP Blocklist Feed

Self-hosted multi-account email client with support for JMAP/IMAP/SMTP, direct integration with Gmail and Outlook APIs. Also Contacts and Calendar. Built with Go, templ, and HTMX, SQLite for storage

Open-source email API for applications and AI agents. Managed hosting at e2a.dev, or self-host with Docker.

High throughput Go SMTP pool library with graceful handling of idle timeouts, errors, and retries.

Eventum Issue Tracking System

Rust implementation of catapulte email sender

qpsmtpd is a flexible smtpd daemon written in Perl

📮 Email queue extending NodeMailer with multi SMTP transports and horizontally scaled applications support

Local-first mail development environment. Point your app at localhost and inspect every message, protocol trace and delivery outcome. SMTP, IMAP, POP3 and a REST API in one self-contained binary.

Laravel mail over HTTPS: send through the SendGrid or Brevo API when SMTP ports 25/465/587 are blocked on DigitalOcean, AWS, Google Cloud or Hetzner. No code changes.