smtp-probe

An open-source email deliverability diagnostic tool — check SPF/DKIM/DMARC, verify addresses via SMTP, and scan IPs against 29 RBL blacklists.

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🚀 Installation

Install smtp-probe in seconds

⚡ Quickstart

Run your first diagnostic in 5 minutes

📖 Guide

In-depth guides for every feature

📋 API Reference

CLI and HTTP API complete reference

Why smtp-probe?

One tool, all diagnostics — DNS records, SMTP verification, IP health, and blacklist scanning in a single binary
Production-ready — IP pool management with auto-failover, multi-node GeoIP routing, HTTP API for programmatic use
Zero dependencies — Single Go binary, deploy anywhere on bare metal or any Linux/macOS server
Open source — MIT licensed, self-hosted, no vendor lock-in

Quick Example

# Check domain DNS configuration
$ smtp-probe check gmail.com
Domain: gmail.com
Score:  95/100

SPF:    ✅ v=spf1 redirect=_spf.google.com
DKIM:   ✅ s=google d=gmail.com
DMARC:  ✅ p=reject sp=reject
MX:     ✅ gmail-smtp-in.l.google.com (pref 5)
PTR:    ✅ No record

# Verify an email address (requires port 25)
$ smtp-probe verify user@example.com
Result: Accepted (250 2.1.5 OK)

# Scan IP against 29 blacklists
$ smtp-probe blacklist 1.2.3.4
Checked 29 blacklists: 0 listed

Get Started →