How to test an SMTP server's greeting

1. Enter the SMTP host

   Type the SMTP host (e.g. mail.example.com) into the "SMTP host" field. Up to 253 characters. Private IPs are rejected.

2. Pick the port

   Port defaults to 25 (the relay port). Common alternatives: 587 (submission with STARTTLS), 465 (implicit TLS / SMTPS). The probe is plain-text TCP, no TLS upgrade.

3. Press Run

   Our server opens a TCP connection, waits for the SMTP banner, sends EHLO toolsina.com, and captures the multi-line response. The session is closed after ~4 seconds.

4. Read the transcript

   Output is a transcript array — server greeting plus capability lines (250-PIPELINING, 250-SIZE, 250-STARTTLS, 250-AUTH, etc.). Missing STARTTLS means the host won't upgrade to TLS on this port; missing AUTH usually means no authenticated relay.