SMTP Handshake Test
Enter a domain to test the external mail delivery path.
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Enter a domain to test the external mail delivery path.
When emails get stuck in your outbox or refuse to send entirely, the issue usually lies in the connection between your mail client and the server. Our SMTP Handshake tool acts like a digital technician, reaching out to your mail host over the network to verify if it is accepting connections, responding to commands, or blocking your traffic completely.
Not all email traffic flows through the same channel. Port 25 is traditionally used for server-to-server relay, but many ISPs and Wi-Fi networks block it to prevent spam. If your emails are failing to send from an office or hotel network, testing alternate submission ports like Port 587 (TLS) or Port 465 (SSL) can instantly reveal if a local firewall is restricting your external mail traffic.
A failed connection doesn't always mean your hosting server is completely down. By reading the live terminal output from our diagnostic tool, you can see exactly where the handshake drops. Whether it is a hard connection refusal, an SSL certificate mismatch, or an unexpected authentication timeout, our tool provides actionable insight so you know exactly what to tell your IT team.
Watch the live server response logs exactly as they happen. See the initial handshake, banner response, and network latency in plain text.
Easily switch between standard unencrypted ports and secure SSL/TLS submission ports to isolate firewall and ISP routing blocks.
If our engine detects a known configuration issue or a blocked port, it automatically generates a "Technician's Insight" to guide your next steps.
If your handshake tests are failing or you cannot restore your mail flow, our IT engineers can diagnose the server routing and get your business back online.
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