SMTP host and port
Use your provider's outgoing mail server. Port 587 normally uses STARTTLS, while port 465 normally uses direct TLS. Port 25 may be blocked by hosting providers.
Live SMTP connection checker Unlimited · one account at a time
Free SMTP Tester Online
Test an SMTP server, port, login, and TLS connection from your browser. Run unlimited free checks one account at a time, with no sign-up and no saved password.
SMTP authentication
Port and TLS handshake
Optional single test message
Diagnostic result
Ready for a connection check
Enter one account, confirm authorization, and run the SMTP server test. This public tool does not test bulk lists.
SMTP authentication test
The tester verifies DNS resolution, the TLS handshake, and SMTP credentials. Authentication errors are separated from connection timeouts and certificate problems.
Test email delivery
Enable the optional message to check whether the authenticated relay accepts one message for your recipient. It is not a bulk sender or inbox-placement guarantee.
SMTP testing guide
A free online SMTP checker for real mail servers
LocalSMTP's free SMTP test tool helps developers, agencies, and email operators troubleshoot outgoing mail before launching an application or campaign. Test Gmail SMTP, Microsoft 365 SMTP, Zoho SMTP, a custom domain SMTP server, or another public relay by entering its hostname, port, username, and password or app-specific password.
What this SMTP tester checks
- Public DNS resolution for the SMTP hostname
- TLS or STARTTLS negotiation on the selected port
- SMTP username and password authentication
- Optional acceptance of one test-recipient email
- Sanitized error guidance for common SMTP failures
Common SMTP test errors
A rejected login usually means an incorrect password, a required app password, or disabled SMTP AUTH. A timeout may indicate the wrong port or a provider firewall. A certificate error can indicate a hostname mismatch or an outdated server certificate.
Open the full mailer workspaceSMTP tester FAQ
Is this SMTP tester really free?
Yes. LocalSMTP provides unlimited free SMTP connection checks, one account at a time, without requiring an account or payment. The optional test email is limited to the single message you request for that check.
What information do I need to test an SMTP server?
You need the sender email, SMTP hostname, port, username, password or app-specific password, and sender name. Add a recipient only when you want to send the optional single test message.
Which SMTP ports and encryption methods are supported?
The tester supports common SMTP ports 587 for STARTTLS, 465 for direct TLS, 25, and 2525 when the server accepts them. The selected port determines the connection mode.
Can I test Gmail SMTP or Microsoft 365 SMTP?
Yes. Enter the SMTP settings supplied by Gmail, Microsoft 365, Zoho, your hosting company, or another public mail provider. Gmail and Microsoft 365 commonly require an app password or an account policy that permits SMTP authentication.
Does LocalSMTP store my SMTP password?
No. The public tester sends the credentials to the server over HTTPS for the live connection check and does not save the account, password, mailbox contents, or test result as a user record.