Email body should be encoded as 'quoted-printable' (#31)

* The body of the mail is encoded with 'quoted-printable'.

Signed-off-by: Cyril GY <cyril.gy@gmail.com>

* Added a unit test to validate the 'quoted-printable' encoding.

Signed-off-by: Cyril GY <cyril.gy@gmail.com>

mime.go

@@ -6,6 +6,7 @@ import (
 	"fmt"
 	"io"
 	"mime/multipart"
+	"mime/quotedprintable"
 	"net/textproto"
 )
 
@@ -142,12 +143,17 @@ func (m *MailYak) writeBody(w io.Writer, boundary string) error {
 		c := fmt.Sprintf("%s; charset=UTF-8", ctype)
 
 		var part io.Writer
-		part, err = alt.CreatePart(textproto.MIMEHeader{"Content-Type": {c}})
+		part, err = alt.CreatePart(textproto.MIMEHeader{"Content-Type": {c}, "Content-Transfer-Encoding": {"quoted-printable"}})
 		if err != nil {
 			return
 		}
 
-		_, err = part.Write(data)
+		var buf bytes.Buffer
+		qpw := quotedprintable.NewWriter(&buf)
+		_, err = qpw.Write(data)
+		qpw.Close()
+
+		_, err = part.Write(buf.Bytes())
 	}
 
 	writePart("text/plain", m.plain.Bytes())

mime_test.go

@@ -227,23 +227,31 @@ func TestMailYakWriteBody(t *testing.T) {
 			"HTML",
 			"",
 			"t",
-			"--t\r\nContent-Type: text/html; charset=UTF-8\r\n\r\nHTML\r\n--t--\r\n",
+			"--t\r\nContent-Transfer-Encoding: quoted-printable\r\nContent-Type: text/html; charset=UTF-8\r\n\r\nHTML\r\n--t--\r\n",
 			false,
 		},
 		{
 			"Plain text",
 			"",
 			"Plain",
 			"t",
-			"--t\r\nContent-Type: text/plain; charset=UTF-8\r\n\r\nPlain\r\n--t--\r\n",
+			"--t\r\nContent-Transfer-Encoding: quoted-printable\r\nContent-Type: text/plain; charset=UTF-8\r\n\r\nPlain\r\n--t--\r\n",
 			false,
 		},
 		{
 			"Both",
 			"HTML",
 			"Plain",
 			"t",
-			"--t\r\nContent-Type: text/plain; charset=UTF-8\r\n\r\nPlain\r\n--t\r\nContent-Type: text/html; charset=UTF-8\r\n\r\nHTML\r\n--t--\r\n",
+			"--t\r\nContent-Transfer-Encoding: quoted-printable\r\nContent-Type: text/plain; charset=UTF-8\r\n\r\nPlain\r\n--t\r\nContent-Transfer-Encoding: quoted-printable\r\nContent-Type: text/html; charset=UTF-8\r\n\r\nHTML\r\n--t--\r\n",
+			false,
+		},
+		{
+			"Both with long lines",
+			"Lorem ipsum dolor sit amet, consectetur adipiscing elit, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua. Ut enim ad minim veniam, quis nostrud exercitation ullamco laboris nisi ut aliquip ex ea commodo consequat. Duis aute irure dolor in reprehenderit in voluptate velit esse cillum dolore eu fugiat nulla pariatur. Excepteur sint occaecat cupidatat non proident, sunt in culpa qui officia deserunt mollit anim id est laborum.",
+			"Lorem ipsum dolor sit amet, consectetur adipiscing elit, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua. Ut enim ad minim veniam, quis nostrud exercitation ullamco laboris nisi ut aliquip ex ea commodo consequat. Duis aute irure dolor in reprehenderit in voluptate velit esse cillum dolore eu fugiat nulla pariatur. Excepteur sint occaecat cupidatat non proident, sunt in culpa qui officia deserunt mollit anim id est laborum.",
+			"t",
+			"--t\r\nContent-Transfer-Encoding: quoted-printable\r\nContent-Type: text/plain; charset=UTF-8\r\n\r\nLorem ipsum dolor sit amet, consectetur adipiscing elit, sed do eiusmod tem=\r\npor incididunt ut labore et dolore magna aliqua. Ut enim ad minim veniam, q=\r\nuis nostrud exercitation ullamco laboris nisi ut aliquip ex ea commodo cons=\r\nequat. Duis aute irure dolor in reprehenderit in voluptate velit esse cillu=\r\nm dolore eu fugiat nulla pariatur. Excepteur sint occaecat cupidatat non pr=\r\noident, sunt in culpa qui officia deserunt mollit anim id est laborum.\r\n--t\r\nContent-Transfer-Encoding: quoted-printable\r\nContent-Type: text/html; charset=UTF-8\r\n\r\nLorem ipsum dolor sit amet, consectetur adipiscing elit, sed do eiusmod tem=\r\npor incididunt ut labore et dolore magna aliqua. Ut enim ad minim veniam, q=\r\nuis nostrud exercitation ullamco laboris nisi ut aliquip ex ea commodo cons=\r\nequat. Duis aute irure dolor in reprehenderit in voluptate velit esse cillu=\r\nm dolore eu fugiat nulla pariatur. Excepteur sint occaecat cupidatat non pr=\r\noident, sunt in culpa qui officia deserunt mollit anim id est laborum.\r\n--t--\r\n",
 			false,
 		},
 	}
@@ -309,7 +317,7 @@ func TestMailYakBuildMime(t *testing.T) {
 			"",
 			"",
 			"",
-			"From: \r\nMime-Version: 1.0\r\nDate: " + now + "\r\nSubject: \r\nTo: \r\nContent-Type: multipart/mixed;\r\n\tboundary=\"mixed\"; charset=UTF-8\r\n\r\n--mixed\r\nContent-Type: multipart/alternative;\r\n\tboundary=\"alt\"\r\n\r\n--alt\r\nContent-Type: text/html; charset=UTF-8\r\n\r\nHTML\r\n--alt--\r\n\r\n--mixed--\r\n",
+			"From: \r\nMime-Version: 1.0\r\nDate: " + now + "\r\nSubject: \r\nTo: \r\nContent-Type: multipart/mixed;\r\n\tboundary=\"mixed\"; charset=UTF-8\r\n\r\n--mixed\r\nContent-Type: multipart/alternative;\r\n\tboundary=\"alt\"\r\n\r\n--alt\r\nContent-Transfer-Encoding: quoted-printable\r\nContent-Type: text/html; charset=UTF-8\r\n\r\nHTML\r\n--alt--\r\n\r\n--mixed--\r\n",
 			false,
 		},
 		{
@@ -321,7 +329,7 @@ func TestMailYakBuildMime(t *testing.T) {
 			"",
 			"",
 			"",
-			"From: \r\nMime-Version: 1.0\r\nDate: " + now + "\r\nSubject: \r\nTo: \r\nContent-Type: multipart/mixed;\r\n\tboundary=\"mixed\"; charset=UTF-8\r\n\r\n--mixed\r\nContent-Type: multipart/alternative;\r\n\tboundary=\"alt\"\r\n\r\n--alt\r\nContent-Type: text/plain; charset=UTF-8\r\n\r\nPlain\r\n--alt--\r\n\r\n--mixed--\r\n",
+			"From: \r\nMime-Version: 1.0\r\nDate: " + now + "\r\nSubject: \r\nTo: \r\nContent-Type: multipart/mixed;\r\n\tboundary=\"mixed\"; charset=UTF-8\r\n\r\n--mixed\r\nContent-Type: multipart/alternative;\r\n\tboundary=\"alt\"\r\n\r\n--alt\r\nContent-Transfer-Encoding: quoted-printable\r\nContent-Type: text/plain; charset=UTF-8\r\n\r\nPlain\r\n--alt--\r\n\r\n--mixed--\r\n",
 			false,
 		},
 		{