Question 1

What does this SMTP tester actually check?

Accepted Answer

This SMTP tester connects to the host and port you provide, records the banner, attempts STARTTLS if requested, and tests SMTP authentication when credentials are supplied. It also returns a transcript so you can see where the flow failed.

Question 2

Should I use port 587 or 465?

Accepted Answer

Use the submission mode your provider documents. Port 587 usually pairs with STARTTLS, while 465 is typically implicit TLS. Port 25 is often filtered and is rarely the right choice for application mail.

Question 3

Do I need to provide from and to addresses?

Accepted Answer

No. Basic connectivity, TLS, and auth checks can run without them. Add envelope addresses when you want the diagnostic to probe more of the submission path after connection and login.

Question 4

Does a healthy SMTP test guarantee inbox placement?

Accepted Answer

No. SMTP health confirms transport setup, not sender reputation or mailbox placement. Pair it with reverse DNS, sender-auth checks, blacklist review, and real mailbox testing before rollout.

Free SMTP tester for connection, STARTTLS, and auth diagnostics

Connect to the SMTP server and inspect the critical transport steps