Merge pull request #441 from wneessen/bug/440_double-quoted-printable-encoding-in-non-ascii-reply-to-addresses

BREAKING CHANGE: Refactor Reply-To header handling.

Author: wneessen

header.go

@@ -76,9 +76,6 @@ const (
 	// HeaderReferences is the "References" header field.
 	HeaderReferences Header = "References"
 
-	// HeaderReplyTo is the "Reply-To" header field.
-	HeaderReplyTo Header = "Reply-To"
-
 	// HeaderSubject is the "Subject" header field.
 	HeaderSubject Header = "Subject"
 
@@ -115,6 +112,9 @@ const (
 	// HeaderFrom is the "From" header field.
 	HeaderFrom AddrHeader = "From"
 
+	// HeaderReplyTo is the "Reply-To" header field.
+	HeaderReplyTo AddrHeader = "Reply-To"
+
 	// HeaderTo is the "Receipient" header field.
 	HeaderTo AddrHeader = "To"
 )

header_test.go

@@ -36,7 +36,6 @@ var (
 		{"Header: Precedence", HeaderPrecedence, "Precedence"},
 		{"Header: Priority", HeaderPriority, "Priority"},
 		{"Header: References", HeaderReferences, "References"},
-		{"Header: Reply-To", HeaderReplyTo, "Reply-To"},
 		{"Header: Subject", HeaderSubject, "Subject"},
 		{"Header: User-Agent", HeaderUserAgent, "User-Agent"},
 		{"Header: X-Auto-Response-Suppress", HeaderXAutoResponseSuppress, "X-Auto-Response-Suppress"},
@@ -53,6 +52,7 @@ var (
 		{"To", HeaderTo, "To"},
 		{"Cc", HeaderCc, "Cc"},
 		{"Bcc", HeaderBcc, "Bcc"},
+		{"Reply-To", HeaderReplyTo, "Reply-To"},
 	}
 )
 

msg.go

@@ -988,12 +988,7 @@ func (m *Msg) BccFromString(rcpts string) error {
 // References:
 //   - https://datatracker.ietf.org/doc/html/rfc5322#section-3.6.2
 func (m *Msg) ReplyTo(addr string) error {
-	replyTo, err := mail.ParseAddress(addr)
-	if err != nil {
-		return fmt.Errorf("failed to parse reply-to address: %w", err)
-	}
-	m.SetGenHeader(HeaderReplyTo, replyTo.String())
-	return nil
+	return m.SetAddrHeader(HeaderReplyTo, addr)
 }
 
 // ReplyToFormat sets the "Reply-To" address for the Msg using the provided name and email address, specifying

msg_test.go

@@ -1530,7 +1530,7 @@ func TestMsg_ReplyTo(t *testing.T) {
 		if err := message.ReplyTo("toni.tester@example.com"); err != nil {
 			t.Fatalf("failed to set ReplyTo: %s", err)
 		}
-		checkGenHeader(t, message, HeaderReplyTo, "ReplyTo", 0, 1, "<toni.tester@example.com>")
+		checkAddrHeader(t, message, HeaderReplyTo, "ReplyTo", 0, 1, "toni.tester@example.com", "")
 	})
 	t.Run("ReplyTo with invalid address", func(t *testing.T) {
 		message := NewMsg()
@@ -1578,7 +1578,7 @@ func TestMsg_ReplyToFormat(t *testing.T) {
 		if err := message.ReplyToFormat("Tina Tester", "tina.tester@example.com"); err != nil {
 			t.Fatalf("failed to set ReplyTo: %s", err)
 		}
-		checkGenHeader(t, message, HeaderReplyTo, "ReplyToFormat", 0, 1, `"Tina Tester" <tina.tester@example.com>`)
+		checkAddrHeader(t, message, HeaderReplyTo, "ReplyToFormat", 0, 1, "tina.tester@example.com", "Tina Tester")
 	})
 	t.Run("ReplyToFormat with invalid address", func(t *testing.T) {
 		message := NewMsg()
@@ -1589,6 +1589,29 @@ func TestMsg_ReplyToFormat(t *testing.T) {
 			t.Errorf("ReplyToFormat should fail with invalid address")
 		}
 	})
+	// https://github.com/wneessen/go-mail/issues/440
+	t.Run("ReplyToFormat with special characters must not double encode", func(t *testing.T) {
+		message := NewMsg()
+		if message == nil {
+			t.Fatal("message is nil")
+		}
+		if err := message.ReplyToFormat("Töni Tester", "töni.tester@example.com"); err != nil {
+			t.Errorf("failed to set ReplyTo: %s", err)
+		}
+		buffer := bytes.NewBuffer(nil)
+		if _, err := message.WriteTo(buffer); err != nil {
+			t.Errorf("failed to write message to buffer: %s", err)
+		}
+		header := strings.Split(buffer.String(), "Reply-To: ")
+		if len(header) != 2 {
+			t.Fatalf("could not split message after Reply-To:")
+		}
+		want := `=?utf-8?q?T=C3=B6ni_Tester?= <töni.tester@example.com>`
+		got := strings.TrimSpace(header[1])
+		if got != want {
+			t.Errorf("Reply-To header does not match: got %q, want %q", got, want)
+		}
+	})
 }
 
 func TestMsg_Subject(t *testing.T) {

msgwriter.go

@@ -118,7 +118,7 @@ func (mw *msgWriter) writeMsg(msg *Msg) {
 	}
 
 	// Set the rest of the address headers
-	for _, to := range []AddrHeader{HeaderTo, HeaderCc} {
+	for _, to := range []AddrHeader{HeaderTo, HeaderCc, HeaderReplyTo} {
 		if addresses, ok := msg.addrHeader[to]; ok {
 			var val []string
 			for _, addr := range addresses {