Email Server Tester

A sysadmin's mail-server probe. Email Server Tester connects to any SMTP host, optionally negotiates TLS, authenticates if you give it credentials, and sends a test message — printing every line of the SMTP conversation so you can pinpoint where delivery breaks.

What it does

Enter SMTP host, port, TLS preference, sender, recipient. Optionally authentication credentials. The tool connects, performs HELO/EHLO, upgrades to TLS if requested, authenticates, and walks through MAIL FROM / RCPT TO / DATA. Every server response is logged. If the conversation fails, you can see which step broke.

When you need it

• "Why aren't password-reset emails going out?"
• Verifying a new SMTP relay before pointing your app at it
• Confirming TLS is actually negotiated, not just available
• Diagnosing SPF, DKIM, or relay-blocking errors at the SMTP level
• Testing whether a mail server still accepts your auth credentials

Features

• Plain and STARTTLS SMTP
• Implicit-TLS (port 465) support
• PLAIN and LOGIN auth methods
• Full SMTP conversation log
• Configurable HELO name, sender, recipient, subject, body
• Portable single executable

System requirements

• Windows 7, 8, 10, 11
• An internet connection (or LAN access to the SMTP host)
• About 1 MB of disk space