From d7294067b867578fbea56a07541dcd0c851e5c41 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Mateusz=20Czapli=C5=84ski?= <czapkofan@gmail.com>
Date: Tue, 20 Jan 2015 13:15:52 +0100
Subject: [PATCH] Fix to emit at most 76 chars per line

From RFC 2045 (and also from looking at other packages), it appears that
line length limit is actually 76 characters, not 78. Also, this fixes
attachments broken before for a certain webmail client (roundcube).

Closes #18.
---
 export.go      |  9 +++++----
 gomail_test.go | 24 ++++++++++++------------
 2 files changed, 17 insertions(+), 16 deletions(-)

diff --git a/export.go b/export.go
index 328b4bb..fd1c3dd 100644
--- a/export.go
+++ b/export.go
@@ -174,10 +174,11 @@ func (w *messageWriter) export() *mail.Message {
 	return &mail.Message{Header: w.header, Body: w.buf}
 }
 
-// As defined in RFC 5322, 2.1.1.
-const maxLineLen = 78
+// As required by RFC 2045, 6.7. (page 21) for quoted-printable, and
+// RFC 2045, 6.8. (page 25) for base64.
+const maxLineLen = 76
 
-// base64LineWriter limits text encoded in base64 to 78 characters per line
+// base64LineWriter limits text encoded in base64 to 76 characters per line
 type base64LineWriter struct {
 	w       io.Writer
 	lineLen int
@@ -203,7 +204,7 @@ func (w *base64LineWriter) Write(p []byte) (int, error) {
 	return n + len(p), nil
 }
 
-// qpLineWriter limits text encoded in quoted-printable to 78 characters per
+// qpLineWriter limits text encoded in quoted-printable to 76 characters per
 // line
 type qpLineWriter struct {
 	w       io.Writer
diff --git a/gomail_test.go b/gomail_test.go
index 8b741e0..41b4864 100644
--- a/gomail_test.go
+++ b/gomail_test.go
@@ -432,13 +432,13 @@ func TestQpLineLength(t *testing.T) {
 	msg.SetHeader("From", "from@example.com")
 	msg.SetHeader("To", "to@example.com")
 	msg.SetBody("text/plain",
-		strings.Repeat("0", 79)+"\r\n"+
-			strings.Repeat("0", 78)+"à\r\n"+
-			strings.Repeat("0", 77)+"à\r\n"+
+		strings.Repeat("0", 77)+"\r\n"+
 			strings.Repeat("0", 76)+"à\r\n"+
 			strings.Repeat("0", 75)+"à\r\n"+
-			strings.Repeat("0", 78)+"\r\n"+
-			strings.Repeat("0", 79)+"\n")
+			strings.Repeat("0", 74)+"à\r\n"+
+			strings.Repeat("0", 73)+"à\r\n"+
+			strings.Repeat("0", 76)+"\r\n"+
+			strings.Repeat("0", 77)+"\n")
 
 	want := message{
 		from: "from@example.com",
@@ -448,13 +448,13 @@ func TestQpLineLength(t *testing.T) {
 			"Content-Type: text/plain; charset=UTF-8\r\n" +
 			"Content-Transfer-Encoding: quoted-printable\r\n" +
 			"\r\n" +
-			strings.Repeat("0", 78) + "=\r\n0\r\n" +
-			strings.Repeat("0", 78) + "=\r\n=C3=A0\r\n" +
-			strings.Repeat("0", 77) + "=\r\n=C3=A0\r\n" +
+			strings.Repeat("0", 76) + "=\r\n0\r\n" +
 			strings.Repeat("0", 76) + "=\r\n=C3=A0\r\n" +
-			strings.Repeat("0", 75) + "=C3=\r\n=A0\r\n" +
-			strings.Repeat("0", 78) + "\r\n" +
-			strings.Repeat("0", 78) + "=\r\n0\n",
+			strings.Repeat("0", 75) + "=\r\n=C3=A0\r\n" +
+			strings.Repeat("0", 74) + "=\r\n=C3=A0\r\n" +
+			strings.Repeat("0", 73) + "=C3=\r\n=A0\r\n" +
+			strings.Repeat("0", 76) + "\r\n" +
+			strings.Repeat("0", 76) + "=\r\n0\n",
 	}
 
 	testMessage(t, msg, 0, want)
@@ -474,7 +474,7 @@ func TestBase64LineLength(t *testing.T) {
 			"Content-Type: text/plain; charset=UTF-8\r\n" +
 			"Content-Transfer-Encoding: base64\r\n" +
 			"\r\n" +
-			strings.Repeat("MDAw", 19) + "MA\r\n==",
+			strings.Repeat("MDAw", 19) + "\r\nMA==",
 	}
 
 	testMessage(t, msg, 0, want)