dns: add HELO/PTR consistency check

Compare the HELO/EHLO hostname announced by the sending server (first
Received hop) against the sender IP's PTR records, surfacing the same
signal as x-ptr/policy.ptr in Authentication-Results. Adds helo_hostname
and helo_ptr_match to DNSResults, applies a 15-point PTR sub-score
penalty on mismatch, and displays the result in a new HELO/PTR
Consistency card.

pkg/analyzer/authentication_x_ptr.go

@@ -0,0 +1,61 @@
+// This file is part of the happyDeliver (R) project.
+// Copyright (c) 2025-2026 happyDomain
+// Authors: Pierre-Olivier Mercier, et al.
+//
+// This program is offered under a commercial and under the AGPL license.
+// For commercial licensing, contact us at <contact@happydomain.org>.
+//
+// For AGPL licensing:
+// This program is free software: you can redistribute it and/or modify
+// it under the terms of the GNU Affero General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// This program is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU Affero General Public License for more details.
+//
+// You should have received a copy of the GNU Affero General Public License
+// along with this program.  If not, see <https://www.gnu.org/licenses/>.
+
+package analyzer
+
+import (
+	"regexp"
+	"strings"
+
+	"git.happydns.org/happyDeliver/internal/model"
+	"git.happydns.org/happyDeliver/internal/utils"
+)
+
+// parseXPtrResult parses the x-ptr result from Authentication-Results.
+// Example: x-ptr=fail smtp.helo=relay.example.org policy.ptr=mail.example.com
+func (a *AuthenticationAnalyzer) parseXPtrResult(part string) *model.XPtrResult {
+	result := &model.XPtrResult{}
+
+	// Extract result (pass, fail, none, temperror, permerror)
+	re := regexp.MustCompile(`x-ptr=(\w+)`)
+	if matches := re.FindStringSubmatch(part); len(matches) > 1 {
+		resultStr := strings.ToLower(matches[1])
+		result.Result = model.XPtrResultResult(resultStr)
+	}
+
+	// Extract announced HELO hostname (smtp.helo)
+	heloRe := regexp.MustCompile(`smtp\.helo=([^\s;()]+)`)
+	if matches := heloRe.FindStringSubmatch(part); len(matches) > 1 {
+		helo := matches[1]
+		result.Helo = &helo
+	}
+
+	// Extract reverse DNS hostname (policy.ptr)
+	ptrRe := regexp.MustCompile(`policy\.ptr=([^\s;()]+)`)
+	if matches := ptrRe.FindStringSubmatch(part); len(matches) > 1 {
+		ptr := matches[1]
+		result.Ptr = &ptr
+	}
+
+	result.Details = utils.PtrTo(strings.TrimPrefix(part, "x-ptr="))
+
+	return result
+}