Rewrite of SendMail function

The SendMail function is rewritten and has the following new functionality:
 - It is optional to skip verification of keys. The config option SKIP_VERIFY is added
 - If the port is 465, or ending on 465, the TLS(/SSL) connection is started first.

conf/app.ini

@@ -94,7 +94,10 @@ SUBJECT = %(APP_NAME)s
 ; Mail server
 ; Gmail: smtp.gmail.com:587
 ; QQ: smtp.qq.com:25
+; Note, if the port ends with "465", SMTPS will be used. Using STARTTLS on port 587 is recommended per RFC 6409. If the server supports STARTTLS it will always be used.
 HOST =
+; Do not verify the certificate of the server. Only use this for self-signed certificates
+SKIP_VERIFY = 
 ; Mail from address
 FROM =
 ; Mailer user name and password

modules/mailer/mailer.go

@@ -67,22 +67,53 @@ func processMailQueue() {
 }
 
 // sendMail allows mail with self-signed certificates.
-func sendMail(hostAddressWithPort string, auth smtp.Auth, from string, recipients []string, msgContent []byte) error {
+func sendMail(settings *setting.Mailer, from string, recipients []string, msgContent []byte) error {
-	client, err := smtp.Dial(hostAddressWithPort)
+	host, port, err := net.SplitHostPort(settings.Host)
 	if err != nil {
 		return err
 	}
 
-	host, _, _ := net.SplitHostPort(hostAddressWithPort)
+	if len(port) == 0 {
-	tlsConn := &tls.Config{
+		port = "587"
-		InsecureSkipVerify: true,
+	}
+
+	tlsconfig := &tls.Config{
+		InsecureSkipVerify: settings.SkipVerify,
 		ServerName:         host,
 	}
-	if err = client.StartTLS(tlsConn); err != nil {
+
+	var conn net.Conn
+	if conn, err = net.Dial("tcp", net.JoinHostPort(host, port)); err != nil {
+		return err
+	}
+	defer conn.Close()
+
+	connection_secure := false
+	// Start TLS directly if the port ends with 465 (SMTPS protocol)
+	if strings.HasSuffix(port, "465") {
+		conn = tls.Client(conn, tlsconfig)
+		connection_secure = true
+	}
+
+	var client *smtp.Client
+	if client, err = smtp.NewClient(conn, host); err != nil {
 		return err
 	}
 
-	if ok, _ := client.Extension("AUTH"); ok && auth != nil {
+	// If not using SMTPS, alway use STARTTLS if available
+	has_starttls, _ := client.Extension("STARTTLS")
+	if !connection_secure && has_starttls {
+		if err = client.StartTLS(tlsconfig); err != nil {
+			return err
+		}
+	}
+
+	auth_available, _ := client.Extension("AUTH")
+
+	// Possible improvement: only plain authentication is now available.
+	// Maybe in future CRAM MD5 as well?
+	if auth_available && len(settings.User) > 0 {
+		auth := smtp.PlainAuth("", settings.User, settings.Passwd, host)
 		if err = client.Auth(auth); err != nil {
 			return err
 		}
@@ -116,7 +147,6 @@ func sendMail(hostAddressWithPort string, auth smtp.Auth, from string, recipient
 // Direct Send mail message
 func Send(msg *Message) (int, error) {
 	log.Trace("Sending mails to: %s", strings.Join(msg.To, "; "))
-	host := strings.Split(setting.MailService.Host, ":")
 
 	// get message body
 	content := msg.Content()
@@ -127,17 +157,12 @@ func Send(msg *Message) (int, error) {
 		return 0, fmt.Errorf("empty email body")
 	}
 
-	var auth smtp.Auth
-	if len(setting.MailService.Passwd) > 0 {
-		auth = smtp.PlainAuth("", setting.MailService.User, setting.MailService.Passwd, host[0])
-	}
-
 	if msg.Massive {
 		// send mail to multiple emails one by one
 		num := 0
 		for _, to := range msg.To {
 			body := []byte("To: " + to + "\r\n" + content)
-			err := sendMail(setting.MailService.Host, auth, msg.From, []string{to}, body)
+			err := sendMail(setting.MailService, msg.From, []string{to}, body)
 			if err != nil {
 				return num, err
 			}
@@ -148,7 +173,7 @@ func Send(msg *Message) (int, error) {
 		body := []byte("To: " + strings.Join(msg.To, ";") + "\r\n" + content)
 
 		// send to multiple emails in one message
-		err := sendMail(setting.MailService.Host, auth, msg.From, msg.To, body)
+		err := sendMail(setting.MailService, msg.From, msg.To, body)
 		if err != nil {
 			return 0, err
 		} else {

modules/setting/setting.go

@@ -437,6 +437,7 @@ type Mailer struct {
 	Host         string
 	From         string
 	User, Passwd string
+	SkipVerify   bool
 }
 
 type OauthInfo struct {
@@ -467,6 +468,7 @@ func newMailService() {
 		Host:       Cfg.MustValue("mailer", "HOST"),
 		User:       Cfg.MustValue("mailer", "USER"),
 		Passwd:     Cfg.MustValue("mailer", "PASSWD"),
+		SkipVerify: Cfg.MustBool("mailer", "SKIP_VERIFY", false),
 	}
 	MailService.From = Cfg.MustValue("mailer", "FROM", MailService.User)
 	log.Info("Mail Service Enabled")