Initial commit

checker/rules_null_mx.go

@@ -0,0 +1,33 @@
+package checker
+
+import (
+	"context"
+
+	sdk "git.happydns.org/checker-sdk-go/checker"
+)
+
+// nullMXRule reports whether the domain declares a null MX (RFC 7505).
+// This is surfaced as a distinct rule so the rest of the rules can short
+// out cleanly: every other rule skips when data.MX.NullMX is true.
+type nullMXRule struct{}
+
+func (r *nullMXRule) Name() string { return "smtp.null_mx" }
+func (r *nullMXRule) Description() string {
+	return "Reports whether the domain publishes a null MX (RFC 7505), which declares it does not accept mail."
+}
+
+func (r *nullMXRule) Evaluate(ctx context.Context, obs sdk.ObservationGetter, _ sdk.CheckerOptions) []sdk.CheckState {
+	data, errSt := loadSMTPData(ctx, obs)
+	if errSt != nil {
+		return []sdk.CheckState{*errSt}
+	}
+	if data.MX.NullMX {
+		return []sdk.CheckState{{
+			Status:  sdk.StatusInfo,
+			Message: "Domain refuses all email via null MX (RFC 7505).",
+			Code:    CodeNullMX,
+			Meta:    map[string]any{"null_mx": true},
+		}}
+	}
+	return []sdk.CheckState{passState("smtp.null_mx.ok", "Domain does not declare a null MX.")}
+}