An SMTP tester verifies whether your mail server is correctly configured. It connects to your SMTP server, authenticates with your credentials, and sends a real test email to confirm everything is working — in seconds.

Port 587 with STARTTLS is the recommended choice for most modern mail servers. Port 465 uses SSL/TLS directly. Port 25 is the original SMTP port but is often blocked by ISPs to prevent spam. Port 2525 is a common alternative when 587 is blocked.

STARTTLS starts as a plain connection then upgrades to encrypted (ports 587, 2525). SSL/TLS starts encrypted from the very beginning (port 465). Both are secure — STARTTLS is more widely supported today.

Common reasons: wrong hostname or port, incorrect username or password, firewall blocking the port, or needing an App Password if 2-step verification is enabled (Gmail, Outlook). Try port 587 with STARTTLS as a first step.

Yes. SMTP Tester does not store, log, or share any of your credentials. Your data is used only to perform the connection test and is discarded immediately after. No accounts, no cookies, no tracking.

Yes. Some internal mail servers or open relays do not require authentication. Simply disable the authentication toggle and enter the host and port to test the connection directly.