Free SMTP Test Tool: Check Email Server Connectivity & Configuration

Diagnose email delivery issues by testing SMTP server connectivity for any email address or domain. Our SMTP test tool performs a comprehensive check including MX record lookup, DNS resolution, port 25/587 connectivity, EHLO handshake, and reverse DNS validation.

Whether you're a developer troubleshooting email delivery, an admin verifying a new mail server setup, or a marketer diagnosing bounce issues, get a full SMTP diagnostic report in seconds.

SMTP Server Test

Enter an email address to perform a full SMTP connectivity and configuration test on its mail servers.

Connecting to mail servers... this may take up to 15 seconds.

{{ result.overall === 'pass' ? 'SMTP OK' : result.overall === 'warn' ? 'SMTP Warning' : 'SMTP Failed' }}

SMTP Test Results for {{ result.domain }}

MX Records

{{ mx.priority }} — {{ mx.host }}

Server IP

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What We Test

What Does Our SMTP Test Check?

Our SMTP test tool runs a comprehensive 6-step diagnostic that mirrors what happens when a real mail server attempts to deliver email to an address.

MX Record Lookup – Verifies mail servers are configured
DNS Resolution – Resolves mail server hostnames to IPs
Port 25 Connectivity – Tests standard SMTP port
Port 587 Connectivity – Tests mail submission port
EHLO Handshake – Validates ESMTP support
Reverse DNS (PTR) – Checks anti-spam PTR record

Common Issues

SMTP Problems This Tool Diagnoses

No MX Records

The domain has no mail servers configured. Every email sent to this address will permanently bounce.

Port 25 Blocked

Many hosting providers block port 25 outbound. The tool helps identify whether this affects reaching the target mail server.

Missing PTR Record

A missing reverse DNS PTR record is a common reason for legitimate emails being marked as spam or rejected outright.

FAQ

Frequently Asked Questions

What is SMTP?

SMTP (Simple Mail Transfer Protocol) is the standard protocol for sending email across the internet. Mail servers use SMTP to send messages between each other. Port 25 is the default SMTP port; port 587 is the submission port used by email clients.

Does this send a test email?

No. Our SMTP test tool performs a connection-level test only. It connects to the mail server, issues an EHLO greeting, and immediately disconnects. No email is sent and the target mailbox is never affected.

Why does the EHLO test sometimes fail?

Some mail servers implement greylisting or reject connections from unknown IP addresses at the EHLO stage. A failed EHLO doesn't always mean the email address is invalid — it can mean the server is being cautious about new connections.

What does 250 OK mean in SMTP?

SMTP response code 250 means the server has accepted the request. During connection tests, a 250 OK response to EHLO means the server is reachable and functioning normally.