Free SMTP Server Test

Verify any SMTP host in seconds—free. Check connectivity, port, TLS/SSL, authentication, and send a real test email to confirm delivery.

Why use this Free SMTP Server test?

Email issues can be sneaky—blocked ports, expired TLS, bad credentials, or a firewall rule. Our Free SMTP Server test runs a live handshake and (optionally) sends a test message so you can pinpoint what’s wrong fast.

- Instant results—no software to install
- Works with any SMTP server or email provider
- Tests ports 25 / 465 / 587 / 2525
- TLS/SSL and STARTTLS checks
- Clear, actionable diagnostics

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How the test works

Email issues can be sneaky—blocked ports, expired TLS, bad credentials, or a firewall rule. Our Free SMTP Server test runs a live handshake and (optionally) sends a test message so you can pinpoint what’s wrong fast.

1. Enter server details – Host (e.g., smtp.example.com), Port, Encryption (None/TLS/SSL/STARTTLS).

2. Add credentials – Username & Password (optional if your server allows IP/relay).

3. Send a test – Choose From/To, Subject, and a quick message.

4. See diagnostics – We show DNS lookup, TCP connect, EHLO/HELO, TLS negotiation, AUTH, MAIL FROM/RCPT TO, DATA, and server codes.

Privacy note: – We only use the credentials to perform your test and do not store them. Use a non-production test account where possible.

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Try it now

SMTP Host: Host (e.g., smtp.example.com), Port, Encryption (None/TLS/SSL/STARTTLS).

Port: 587 (recommended), 465 (SSL), 25 (may be blocked), 2525 (alt)

Encryption: STARTTLS / SSL / None

Username: your full email (often)

Password: app-specific password, if required

From: test@yourdomain.com

To: your personal inbox

Subject: “SMTP Test from smtpprovider.com”

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What your results mean

Connected – We reached the host and port; networking is fine.

TLS OK – A secure channel is established; certificate and ciphers accepted.

Auth OK – Username/password accepted; relaying permitted for your account.

Message Queued / Accepted – Server accepted the email for delivery.

Failure with code – We’ll show the exact SMTP status (e.g., 535, 550) and how to fix it.

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Common SMTP ports (and when to use them)

587 (STARTTLS): Modern default for submission (recommended)

465 (SSL/TLS): Legacy SMTPS; still common and secure

25 (Plain/TLS): Server-to-server relay; often blocked by ISPs/clouds

2525 (STARTTLS): Alternate port supported by many providers

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Quick fixes for frequent SMTP errors

535 5.7.8 Authentication failed
Check username (often full address), reset/app-specific password, ensure AUTH mechanismsupported.

550 5.1.1 User unknown
Recipient address is wrong or mailbox doesn’t exist.

550 5.7.1 Relaying denied
Authenticate or add the sender IP/domain to allowed relays.

454 4.7.0 TLS not available
Switch to a non-TLS port or fix server certificate/config.

421 4.7.0 Temporary rate limit
Slow down tests; check provider sending limits.

Timeout / “Could not connect”
Firewall blocks, wrong host/port, or provider outage. Try 587 or 465, confirm DNS resolves.

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Deliverability tips (after the SMTP test passes)

Publish correct SPF record including your sending hosts

Sign messages with DKIM

Set a DMARC policy (monitoring → enforcement)

Use a valid PTR (reverse DNS) for your server IP

Match HELO/EHLO to a resolvable hostname

Warm up new IPs and keep bounce/complaint rates low

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FAQ: Free SMTP Server test

Is this SMTP test really free?
Yes—basic connectivity, TLS, auth, and a single test email are free.

Do you store my credentials?
No. They’re used only to run your test. Prefer a test account or app-password.

Will this fix deliverability issues?
It verifies your server works. For inbox placement, configure SPF, DKIM, DMARC and monitor reputation.

Which port should I try first?
587 with STARTTLS. If blocked, try 465 (SSL). Avoid 25 for submission.

421 4.7.0 Temporary rate limit
Slow down tests; check provider sending limits.

Can I test without authentication?
Yes, if your server allows IP-based relaying or you’re testing a local relay. Many providers require AUTH.

Why did my test email not arrive?
The server may have accepted it but filtered later. Check spam, quarantine, and your provider’s logs.

Send Better. Choose smtpprovider.

Try Now for Free