Free SMTP Tester — Test Your SMTP Server in Seconds
Enter your SMTP server details below and run a free, instant test. Our SMTP tester connects to your mail server, checks authentication, verifies the port, and confirms whether it can actually send mail.
No signup required. Your credentials are used only to run the test and are never stored.
Server Configuration
Email Settings
What Is an SMTP Tester?
An SMTP tester is an online tool that checks whether your SMTP (Simple Mail Transfer Protocol) server is configured correctly and able to send email. Instead of guessing why your messages bounce or never arrive, you enter your server details and the tool attempts a real connection — exactly the way an email client or application would.
In a single test, an SMTP checker tells you three critical things:
- Can it connect? — Is the server reachable on the port you specified?
- Can it log in? — Are your username, password, and authentication method accepted?
- Can it send? — Will the server actually relay a message for you?
How to Test Your SMTP Server
Running an SMTP test takes less than a minute. Here's how to test SMTP server settings step by step:
- Enter your SMTP host. This is your mail server address, such as
smtp.yourdomain.comor your provider's server. - Choose the port. Common SMTP ports are 587 (TLS), 465 (SSL), 25 (legacy/relay), and 2525 (alternative).
- Add your credentials. Enter the username (usually your full email address) and password or app password.
- Select encryption. Match it to your port — TLS for 587, SSL for 465, or none for an unauthenticated relay test.
- Click "Test Connection." The tool runs the full handshake and shows each step live.
- Read the result. A green "success" confirms your server is working. An error message tells you exactly where the test stopped.
What the SMTP Test Actually Checks
A good SMTP test does more than ping a server. Each stage maps to a real point of failure in email delivery.
Connection Test
The tool opens a socket to your host on the chosen port. If this fails, the cause is almost always a wrong host, closed port, or firewall blocking outbound traffic.
Authentication Test
Next, the tool attempts to log in. A failure here means the username, password, or auth method is wrong — a very common issue after password changes.
Relay & Send Test
Finally, the tool asks the server to accept a message. If refused, you've likely hit a relay restriction — the server won't send mail for your address or IP.
Port & Encryption Check
The test confirms the port is open and that the encryption setting matches what the server expects. A mismatch is one of the most common silent failures.
SMTP Ports Explained
Choosing the right port is half the battle. Here's what each one is for:
Common SMTP Errors and What They Mean
When a test fails, the server returns a code. Here are the ones you'll see most often:
- Connection timed out / refused — Wrong host or port, or a firewall is blocking the connection.
- 535 Authentication failed — Bad username/password, or the provider needs an app password.
- 530 Authentication required — You tried to send without logging in first.
- 550 Relay not permitted — The server won't relay mail for your address or IP.
- 421 Service not available — The server is overloaded, rate-limiting, or temporarily down.
- TLS/SSL handshake failed — Your encryption setting doesn't match the port.
Why You Should Test Your SMTP Server
Email that doesn't send — or sends but lands in spam — is usually a configuration problem, not a mystery. Testing your SMTP server lets you:
- Confirm a new setup works before you point a live application at it.
- Diagnose delivery failures without digging through application logs.
- Verify credentials after a password reset or provider change.
- Check relay and port settings when migrating servers or providers.
- Validate cold email and bulk-sending infrastructure so campaigns actually reach the inbox.
Frequently Asked Questions
How do I test if my SMTP server is working?
Enter your SMTP host, port, username, and password into the tester above and click "Test Connection." The tool connects to your server, attempts to authenticate, and tries to send a test message. A success result confirms your SMTP server is working; an error tells you exactly where it failed.
How do I test an SMTP connection?
Provide the SMTP host and port, then run the test. If the connection step succeeds, your server is reachable. If it times out or is refused, the port is likely closed or a firewall is blocking it — try port 587 or 2525.
How do I test SMTP authentication?
Run the test with your username and password filled in. The authentication step will pass if your credentials and auth method are correct. A "535 authentication failed" error means the login was rejected — check for typos or whether your provider requires an app-specific password.
How do I test an SMTP relay?
Use the tester to attempt sending a message after connecting. If the server returns "550 relay not permitted," it won't relay mail for your address or IP — you'll need to authenticate first or adjust the server's relay settings.
What port should I use to test SMTP?
Start with 587 (TLS), which is the modern standard. If that's blocked, try 465 (SSL) or 2525. Port 25 is mainly for server-to-server relay and is often blocked by ISPs.
Is this SMTP tester free?
Yes. You can run unlimited SMTP tests online for free, with no signup required.
Do you store my SMTP credentials?
No. Your credentials are used only to perform the live test during your session and are not stored on our servers. Optionally, you can save them locally in your browser using the "Save config" checkbox.