SMTP diagnostics

Free SMTP Tester

An SMTP tester checks whether a mail server can accept a connection using the host, port, encryption mode, and optional login credentials you plan to use in production.

Connection report

Run a test to see connection diagnostics.

Public SMTP host

The tester connects only to public SMTP hostnames and blocks private network targets.

TLS mode

Port 587 with STARTTLS is the standard submission setup.

Authentication

Credentials are optional. Without them, the test verifies connection and server greeting only.

Copyable report

SMTP Tester - smtp.example.com:587
Status: pending
Security: STARTTLS

Run a test to generate diagnostics.

Connection diagnostics

Validate DNS resolution, SMTP greeting, selected port, and TLS expectations before debugging app code.

Optional auth check

Include credentials to confirm provider login readiness without sending an email message.

TLS guidance

Compare STARTTLS, implicit TLS, and legacy plain SMTP choices against standard ports.

SMTP Tester FAQ

What is an SMTP tester?

An SMTP tester connects to a mail server and verifies whether the host, port, encryption mode, and optional credentials are ready for sending email.

Which SMTP port should I test first?

Port 587 with STARTTLS is the standard choice for authenticated email submission. Port 465 uses implicit TLS, while port 25 is usually for server-to-server relay and may be blocked.

Does this tool send an email?

No. The tester uses SMTP verification to check the connection and authentication path without sending a message to a recipient.

Should I include my SMTP password?

Only include credentials when you need to verify login readiness. The password is sent only to the target SMTP server during the verification request and is not included in the report.

Why did my SMTP test fail?

Common causes include the wrong port, blocked outbound SMTP traffic, TLS mismatch, DNS issues, invalid credentials, or provider restrictions on the sending account.

Parse inbound email after SMTP is working

MailParse turns received email into structured JSON with webhooks, attachment handling, and developer-friendly logs.

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