A test domain built to be refused

What this domain is for

This domain publishes rules telling every mail system to reject messages that claim to come from it. The Security Foundations email configuration test sends one message from here, “Security Foundations test message”, that is deliberately built to break those rules.

A mail system that honours the rules should refuse it. That refusal is what the test is checking for.

If that message did not reach you

That is the expected result. Your mail system turned away a message that failed its sender’s published rules.

If that message did reach you

It got past a check it should have failed. The message itself is harmless — no links, no attachments, nothing to act on — but the result is worth knowing, and the test’s results explain what it means for your mail setup.