💬 SMTP Connectivity Test

Test SMTP server connectivity and verify mail server configuration for reliable email delivery.

Enter Domain Name:

💡 Tip: Enter your mail domain and click "Test SMTP Connection" to verify server connectivity.

Enter a domain and click "Test SMTP Connection" to view results.

What the test does

This one really connects. Your domain goes to SimpleMoney's network-tools API, which resolves the domain's MX records, takes the first three by priority, and opens a TCP socket to port 25 on each with a five second timeout. When a server answers it reads the opening line - the SMTP banner - and reports it:

example.com  MX  10 mx1.example.com
                 20 mx2.example.com

connect mx1.example.com:25
220 mx1.example.com ESMTP ready

A 220 banner means the server accepted the connection and is ready for a session. The lower MX priority number is the preferred server; senders fall back to higher numbers when it does not answer.

Reading a failure

No MX records stops the test before any connection. A domain with no MX cannot receive mail at all, unless senders fall back to its A record, which many no longer do.
Timeout usually means a firewall is dropping the packets rather than refusing them. A refused connection comes back fast; a filtered one hangs until the five seconds run out.
One host up, another timing out still delivers, because senders retry the backup - but a dead backup MX is a delay waiting to happen.

This checks the receiving path only, on port 25. It does not test submission ports 587 or 465, does not authenticate, and never sends a message - so it cannot tell you whether a given mailbox accepts mail or whether your own outbound mail will be delivered.

Frequently asked questions

What does the 220 line mean?

It is the greeting an SMTP server sends the moment a connection opens, and the numeric 220 is the code for service ready. The text after it usually names the server software, which is why banners are also a small information leak.

Why test port 25 rather than 587?

Port 25 is where servers accept mail from other servers, so it is the port that matters for receiving. Port 587 is for your own users submitting mail with credentials, and most residential and cloud networks block outbound 25 entirely.

My MX record is there but nothing connects. What now?

Check that the MX points at a hostname with an A record rather than an IP address or a CNAME, both invalid in MX data, then check the firewall allows inbound 25.