About SMTP Probe
Built by the uSpeedo email infrastructure team, SMTP Probe is a free tool that gives anyone the power to verify email addresses in real time — the same technology that powers our enterprise-grade email validation API.
Our Mission
Every day, billions of emails bounce because of invalid addresses. We believe email verification should be accessible to everyone — from solo marketers to enterprise engineering teams. SMTP Probe makes professional-grade verification available instantly from any browser, with no signup required.
Core Technology
SMTP Probe connects directly to recipient mail servers using the SMTP protocol to verify mailbox existence without sending any message. Our verification engine performs DNS MX lookups, SMTP RCPT TO validation, and catch-all domain detection — delivering results in seconds with enterprise-grade accuracy.
Why We Built This
Transparency
Open-source verification engine so developers can audit exactly how results are produced.
Privacy First
We never store or log the email addresses you verify. Each probe is ephemeral.
Developer Friendly
Full REST API with batch verification, webhooks, and SDKs available through uSpeedo Console.
Always Free
100 free verifications per day. No credit card, no signup, no surprise paywalls.
Ready to verify emails at scale?
Get Started with uSpeedo API