SMTP test mailer
Send one real test email through your SMTP server to confirm the host, port, encryption and password all work, before you trust them in a contact form or a mail plugin. You see the server's own reply.
- Tests the real SMTP handshake
- App Password and TLS or SSL
- Credentials never stored
Quick fill your provider's settings
Result
Fill in the form to test
- HostWaiting for inputYour mail server
- Connect—Port and encryption
- Sign in—Username and password
- Send—Hand over the message
Test result
Fill in the message and SMTP settings above and send a test. The server's result and the exact settings used appear here, with the server's own error message if it fails.
Fair-use limit: 5 tests per hour and 20 per day for each visitor IP address, to protect this server's reputation.
What a passing test proves, and what it doesn't
SMTP is only the first hop. Knowing where it ends helps you read the result correctly.
It proves the server accepts you
A success means your host, port, encryption and credentials are correct and the server took the message. That rules out the most common cause of "emails are not sending": wrong settings.
It does not prove inbox placement
Whether the message lands in the inbox, spam or nowhere depends on the receiving side and your domain's reputation. A pass plus a spam-foldered test points at DNS, not SMTP.
App Passwords, not your real one
Gmail and most providers block your account password from tools like this. A provider-generated App Password or SMTP key is what the password field expects.
Timeouts are firewalls
If a port never answers, the block is on the network between the servers, not in your password. The fix is a different port or an open firewall, not new credentials.
SMTP ports and the encryption to pair with them
Pick the port your provider lists, and match the encryption. Mismatches are the most common handshake failure.
| Port | Encryption | When to use it |
|---|---|---|
587 |
TLS (STARTTLS) | The modern standard for sending mail. The connection starts in plain text and upgrades to encryption. Try this first. |
465 |
SSL (implicit TLS) | The whole connection is encrypted from the start. A reliable alternative when port 587 is blocked. |
25 |
None or TLS | Server-to-server mail. Blocked for sending by almost every host and cloud provider, so avoid it for tests. |
2525 |
TLS | An unofficial alternative that some providers (SendGrid, Mailgun, Brevo) offer when 587 is blocked by a firewall. |
Common SMTP hosts and settings
A starting point for the biggest providers. Always confirm the current values in your provider's own help pages.
| Provider | Host | Port | Encryption | Sign-in |
|---|---|---|---|---|
| Gmail / Google Workspace | smtp.gmail.com |
587 |
TLS | App Password required |
| Microsoft 365 (business) | smtp.office365.com |
587 |
TLS | OAuth often required |
| Outlook.com / Hotmail | smtp-mail.outlook.com |
587 |
TLS | Modern sign-in required |
| Zoho Mail | smtp.zoho.com |
465 |
SSL | App Password if 2FA is on |
| Hostinger | smtp.hostinger.com |
465 |
SSL | Mailbox password |
| SendGrid | smtp.sendgrid.net |
587 |
TLS | Username "apikey", password = API key |
| Brevo (Sendinblue) | smtp-relay.brevo.com |
587 |
TLS | SMTP key |
| Mailgun | smtp.mailgun.org |
587 |
TLS | SMTP credentials |
How this tool works
What happens between pressing send and reading the result.
Fill in the message
Set a From name and From email on a domain your server is allowed to send for, and a recipient you can check. A personal Gmail recipient is a good way to confirm inbox placement.
Enter the SMTP settings
Host, port, encryption, username and password or App Password, from your email provider. The username and From email usually belong to the same mailbox.
The server connects once
Our server checks the host is public, connects to the exact resolved IP on your port, starts the encryption you chose, signs in and hands over the message.
Read the result
A success means the server accepted the message. A failure shows the server's own response, such as an authentication or timeout error, so you know what to fix.
What this tool does, and what it doesn't
A plain list, so you know exactly what to expect.
This tool does
- Connect to your SMTP server and sign in
- Send one test email through it
- Test TLS, SSL and App Passwords
- Show the server's own error message
- Help you tell a firewall from bad credentials
- Refuse internal and private addresses
This tool does not
- Store or log your credentials
- Act as an open relay or send in bulk
- Check your SPF, DKIM or DMARC records
- Guarantee the message reaches the inbox
- Sign in with OAuth for you
- Need an account or login
Where your data goes
Your SMTP settings and the test message are sent to our server over HTTPS and used only for this one connection. Our server signs in to the mail server you named and hands over the message; your credentials are held in memory for the request and never written to our database or logs. The test email itself goes to the recipient through your provider. Like any website, our server may keep normal access logs, as described in our privacy policy.
Microsoft explains its move away from basic SMTP sign-in and what to use instead.
Common results and what they mean
The six outcomes people see most, and what each one is telling you.
Authentication failed (535)
The username or password is wrong, or the provider blocks password sign-in. For Gmail use an App Password; for Microsoft, basic sign-in is being retired in favour of OAuth.
Connection timed out
The port did not answer. A firewall on your host or network is blocking it, not a bad password. Try port 465, or ask your host to open outbound SMTP.
Certificate or TLS error
The encryption did not match the port. Pair 587 with TLS or 465 with SSL, and make sure the host name is spelled exactly as your provider lists it.
Accepted but lands in spam
The server accepted it, but the receiving side does not trust your domain. Publish SPF, DKIM and DMARC and send from an authorised address.
From address rejected
The server will not send as an address it does not own. Use a From email on a domain this mail server is allowed to send for.
Works here, fails in your plugin
Your credentials are fine, so the problem is in the plugin or site config, not the mail server. Re-enter the same settings in your SMTP plugin.
Questions about testing SMTP
What does this tool actually test?
It checks one thing: that your SMTP server accepts your credentials and hands off a message. Our server connects to the host, port and encryption you enter, signs in with your username and password, and sends a single test email. A success means the server accepted the message for delivery, not that it reached the inbox.
Why does Gmail reject my normal password?
Google blocks sign-ins with your account password from scripts and third-party tools. Turn on 2-Step Verification, then create a 16-character App Password in your Google Account and paste that in the password field. The username stays your full Gmail address.
Does this work with Microsoft 365 and Outlook.com?
Often no longer. Microsoft is retiring basic username-and-password SMTP: personal Outlook.com, Hotmail and Live accounts already require modern sign-in, and Microsoft 365 business tenants are being switched to OAuth, which returns "550 5.7.30 Basic authentication is not supported". A failure here can mean the server is reachable but no longer accepts password sign-in.
What does "Connection timed out" mean?
The port never answered. That is almost always a firewall, not a wrong password. Many shared hosts and cloud servers (AWS, DigitalOcean, Google Cloud) block outbound ports 25 and 587 to stop spam. Try port 465, or ask your host to open outbound SMTP.
Which port and encryption should I pair?
Use port 587 with TLS (STARTTLS) first; it is the modern standard for sending. If 587 is blocked, use port 465 with SSL. Port 25 is for server-to-server mail and is widely blocked for sending. Port 2525 is an unofficial alternative some providers offer. Pairing 587 with SSL, or 465 with TLS, makes the handshake fail.
The test passed but my email still goes to spam. Why?
SMTP authentication proves you may send, not that your domain is trusted. Placement depends on your DNS records. Publish SPF, DKIM and DMARC for your sending domain, and send from an address on a domain your server is allowed to send for. You can check these with our Email Privacy Checker.
Are my SMTP credentials safe?
They travel to our server over HTTPS, are held in memory only for this one test, and are never written to our database or logs. We do not fill them in for you and we never reuse them. Even so, prefer an App Password or a dedicated test account over your main password, and the tool will only connect to public mail servers, never to internal addresses. A hashed, temporary copy of your IP address is used for rate limiting and expires within 24 hours, as described in our privacy policy.