Free SMTP Test ToolMost tools tell you it failed. This one shows you where. Enter your settings, send a single live test, and read the full SMTP transcript, command by command, with the failing step called out.
SMTP TranscriptSomething failed. Maybe auth, maybe TLS, maybe the relay just said no. You won't know from a bounce message. Run an SMTP test and the whole exchange comes back in order, colour coded, with the broken step sitting right there.
FAQHow the tool works, which port to pick, and what the server is telling you when a test fails.
An SMTP test tool connects to your mail server and sends one real message through it, recording every command and reply along the way. Instead of guessing why an email bounced or vanished, you watch the greeting, EHLO, STARTTLS handshake, authentication, and delivery happen step by step, so the exact failing command is on screen.
Enter your SMTP host, port, and connection type, add your username and password if the server requires authentication, then run the test. The tool opens a real connection to your SMTP server, sends a message from your from address to your to address, and shows the full colour-coded transcript as soon as the run finishes.
Yes. One message is delivered from the sender you enter to the recipient you enter, through the SMTP server you specify. Use your own addresses, expect the message to arrive, and check the transcript to confirm the server accepted it for delivery.
Port 587 with STARTTLS is the recommended submission port, port 465 uses implicit SSL, and port 25 is the traditional relay port, often blocked by hosting providers. The tool supports all three, so test the port your application is actually configured to use.
Run a test and read the transcript. A successful run ends with the server accepting the message using a 250 OK reply. Failed authentication shows as a 535 reply, a refused relay as 550 or 553, and a wrong host or port fails before the greeting. Each error points at the exact setting to fix.
The usual causes are wrong credentials, a blocked port, missing STARTTLS, an unverified sender, or a server that refuses to relay for your address. The transcript shows which one it is: the failing command and the server's exact reply appear in the transcript, so you fix the right setting first time.
Blue lines are commands sent from your client to the server. Green lines are replies from the server. Grey lines are informational notes from the debugger, and red lines are errors, highlighted so the failing step stands out.
Most tests finish in a few seconds. Slow servers, greylisting, and DNS timeouts can stretch a run out, and the tool waits up to 3 minutes before giving up. Keep the page open until the transcript appears.
Yes, free with no signup or card required. You get the full transcript in the browser and can download it as a plain text file. Logs are kept for a short period after the run in case you need them again.
Free, no signup required, and each tool shows you the exact response from your mail server so you can see the full details.
FeaturesEverything behind reliable delivery at any volume: sending, verification, routing, and the analytics to see what happened, from first API call to millions a month.
Send transactional and bulk emails through reliable SMTP infrastructure built for speed, security, and deliverability.
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Receive and route incoming emails directly into your applications using flexible automation and processing workflows.
Create and deliver marketing campaigns designed to increase engagement, reach, and customer retention.
Receive real-time event notifications for deliveries, opens, and clicks for storage and automation workflows.
Monitor email performance with detailed insights, reporting tools, and actionable delivery metrics in real time.
Gain greater sending control with dedicated IPs designed for consistency, reputation, scalability, and reliability.
Build integrations faster using SDKs, code examples, and resources for modern application development.
