New SMTP library and refactoring of mailer code

core/mail/mime.go

@@ -0,0 +1,21 @@
+// +build go1.5
+
+package mail
+
+import (
+	"mime"
+	"mime/quotedprintable"
+	"strings"
+)
+
+var newQPWriter = quotedprintable.NewWriter
+
+type mimeEncoder struct {
+	mime.WordEncoder
+}
+
+var (
+	bEncoding     = mimeEncoder{mime.BEncoding}
+	qEncoding     = mimeEncoder{mime.QEncoding}
+	lastIndexByte = strings.LastIndexByte
+)