SMTP Tester

The SMTP Tester validates core mail delivery channel by simulating a standard SMTP session against a configured server. It accepts host, port, credentials, and address fields, and optionally uses TLS. The tool captures connection results, server responses, and timing metrics. By design, it avoids delivering real messages; it focuses on protocol validity and reachable paths. This helps developers, sysadmins, and CI systems quickly identify misconfigurations such as incorrect credentials, blocked ports, or improper TLS setups. The output is structured, enabling automation to proceed with deeper tests or remediation steps.
How it works conceptually: the tool establishes a TCP connection, performs the SMTP handshake, conditionally upgrades to TLS with STARTTLS, authenticates if credentials are provided, and issues a minimal MAIL FROM / RCPT TO sequence to verify relaying permissions. It records latency, server reply codes, and TLS negotiation results. It supports common authentication methods and timeout controls. Optional DNS lookups for MX and host verification enhance reliability. The medium-level outputs are designed for integration with monitoring dashboards and CI pipelines, enabling consistent health checks across environments.
Unique value and use cases: built for automation, it delivers deterministic results suitable for health checks, pre-deployment validations, and incident triage. Use cases include validating staging mail servers, ensuring TLS and authentication configurations, and quick remediation guidance for operators. It complements full mail tests by isolating protocol and network aspects.