feat(PROJ-92,PROJ-93): Weiterleitung in Liste/Detail anzeigen, imap-verify Vollständigkeitsprüfung

PROJ-92: forwarded_via in Suchtreffern, Detail und Threads; Badge im Portal.
PROJ-93: archivmail imap-verify gleicht Message-IDs im IMAP-Postfach mit dem
Archiv ab (strikt lesend, nur Zahlen und Ordner:UID).

Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>

pkg/mailparser/forwarded.go

@@ -0,0 +1,36 @@
+package mailparser
+
+import (
+	"net/mail"
+	"strings"
+)
+
+// Display only: Return-Path is sender-controlled and must never drive access decisions.
+func ForwardedVia(pm *ParsedMail) string {
+	if pm == nil {
+		return ""
+	}
+	rp := normalizeAddress(pm.ReturnPath)
+	if rp == "" || rp == normalizeAddress(pm.From) {
+		return ""
+	}
+	for _, list := range [][]string{pm.To, pm.CC, pm.BCC, pm.DeliveryAddresses} {
+		for _, a := range list {
+			if normalizeAddress(a) == rp {
+				return rp
+			}
+		}
+	}
+	return ""
+}
+
+func normalizeAddress(s string) string {
+	s = strings.TrimSpace(s)
+	if s == "" || s == "<>" {
+		return ""
+	}
+	if a, err := mail.ParseAddress(s); err == nil {
+		return strings.ToLower(strings.TrimSpace(a.Address))
+	}
+	return strings.ToLower(strings.Trim(s, "<>"))
+}

pkg/mailparser/forwarded_test.go

@@ -0,0 +1,135 @@
+package mailparser_test
+
+import (
+	"testing"
+
+	"archivmail/pkg/mailparser"
+)
+
+func parseRaw(t *testing.T, headers string) *mailparser.ParsedMail {
+	t.Helper()
+	pm, err := mailparser.Parse([]byte(headers + "Subject: test\r\n\r\nbody\r\n"))
+	if err != nil {
+		t.Fatalf("Parse: %v", err)
+	}
+	return pm
+}
+
+func TestForwardedVia(t *testing.T) {
+	tests := []struct {
+		name    string
+		headers string
+		want    string
+	}{
+		{
+			name: "forward via cc",
+			headers: "Return-Path: <fwd@example.com>\r\n" +
+				"From: Carol <carol@example.org>\r\n" +
+				"To: dave@example.org\r\n" +
+				"Cc: Fwd <fwd@example.com>\r\n",
+			want: "fwd@example.com",
+		},
+		{
+			name: "forward via envelope-to",
+			headers: "Return-Path: <fwd@example.com>\r\n" +
+				"Envelope-To: fwd@example.com\r\n" +
+				"From: carol@example.org\r\n" +
+				"To: dave@example.org\r\n",
+			want: "fwd@example.com",
+		},
+		{
+			name: "forward via delivered-to",
+			headers: "Return-Path: <fwd@example.com>\r\n" +
+				"Delivered-To: fwd@example.com\r\n" +
+				"From: carol@example.org\r\n" +
+				"To: dave@example.org\r\n",
+			want: "fwd@example.com",
+		},
+		{
+			name: "forward via bcc",
+			headers: "Return-Path: <fwd@example.com>\r\n" +
+				"From: carol@example.org\r\n" +
+				"To: dave@example.org\r\n" +
+				"Bcc: fwd@example.com\r\n",
+			want: "fwd@example.com",
+		},
+		{
+			name: "return-path equals from",
+			headers: "Return-Path: <carol@example.org>\r\n" +
+				"From: Carol <carol@example.org>\r\n" +
+				"To: dave@example.org, carol@example.org\r\n",
+			want: "",
+		},
+		{
+			name: "return-path equals from case-insensitive",
+			headers: "Return-Path: <Carol@Example.ORG>\r\n" +
+				"From: CAROL@example.org\r\n" +
+				"To: carol@example.org\r\n",
+			want: "",
+		},
+		{
+			name: "newsletter bounce address not a recipient",
+			headers: "Return-Path: <bounce-123@mailer.example.net>\r\n" +
+				"From: news@example.net\r\n" +
+				"To: dave@example.org\r\n",
+			want: "",
+		},
+		{
+			name: "no return-path",
+			headers: "From: carol@example.org\r\n" +
+				"To: dave@example.org\r\n",
+			want: "",
+		},
+		{
+			name: "null return-path",
+			headers: "Return-Path: <>\r\n" +
+				"From: carol@example.org\r\n" +
+				"To: dave@example.org\r\n",
+			want: "",
+		},
+		{
+			name: "mixed case recipient",
+			headers: "Return-Path: <Fwd@Example.COM>\r\n" +
+				"From: carol@example.org\r\n" +
+				"To: FWD@example.com\r\n",
+			want: "fwd@example.com",
+		},
+		{
+			name: "multiple recipients",
+			headers: "Return-Path: <fwd@example.com>\r\n" +
+				"From: carol@example.org\r\n" +
+				"To: dave@example.org, Erin <erin@example.org>, fwd@example.com\r\n" +
+				"Cc: frank@example.org\r\n",
+			want: "fwd@example.com",
+		},
+		{
+			name: "multiple recipients without match",
+			headers: "Return-Path: <fwd@example.com>\r\n" +
+				"From: carol@example.org\r\n" +
+				"To: dave@example.org, erin@example.org\r\n" +
+				"Cc: frank@example.org\r\n",
+			want: "",
+		},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			if got := mailparser.ForwardedVia(parseRaw(t, tt.headers)); got != tt.want {
+				t.Errorf("ForwardedVia = %q, want %q", got, tt.want)
+			}
+		})
+	}
+}
+
+func TestForwardedViaDirectFields(t *testing.T) {
+	if got := mailparser.ForwardedVia(nil); got != "" {
+		t.Errorf("nil: got %q", got)
+	}
+	pm := &mailparser.ParsedMail{
+		From:              "carol@example.org",
+		ReturnPath:        "fwd@example.com",
+		DeliveryAddresses: []string{"fwd@example.com"},
+	}
+	if got := mailparser.ForwardedVia(pm); got != "fwd@example.com" {
+		t.Errorf("delivery address: got %q", got)
+	}
+}