SMTP Tester Guide
RookSMTP probes mail servers without sending by default. Optional send mode delivers one message when you supply credentials.
RookSMTP runs from RookVPN’s network, not your laptop. A pass here does not guarantee your ISP allows outbound port 587 at home.
Gmail
Use smtp.gmail.com on port 587 with STARTTLS. Google requires 2-Step Verification and an App Password for SMTP clients.
Microsoft 365
Use smtp.office365.com on port 587. SMTP AUTH can be disabled per mailbox or tenant; a probe failure may be policy.
STARTTLS
The probe reports whether the server offers STARTTLS before authentication. Plaintext AUTH without TLS is a fail.