smtp: Support connect TLS server (#29)

mail/mail.go

@@ -14,29 +14,37 @@ import (
 type Dialer struct {
 	Server   string
 	Port     int
+	TLS      bool
 	Account  string
 	Password string
 	Timeout  time.Duration
 }
 
-func (d *Dialer) Dial() (*smtp.Client, error) {
+func (d *Dialer) Dial() (client *smtp.Client, err error) {
 	if d.Timeout == 0 {
 		d.Timeout = 3 * time.Minute
 	}
 
 	ctx, cancel := context.WithTimeout(context.Background(), d.Timeout)
 	defer cancel()
 
-	client, err := smtp.Dial(ctx, fmt.Sprintf("%s:%d", d.Server, d.Port))
+	if d.TLS {
+		client, err = smtp.DialTLS(ctx, fmt.Sprintf("%s:%d", d.Server, d.Port))
+	} else {
+		client, err = smtp.Dial(ctx, fmt.Sprintf("%s:%d", d.Server, d.Port))
+	}
 	if err != nil {
-		return nil, err
+		return
 	}
-	if ok, _ := client.Extension("STARTTLS"); ok {
-		if err := client.StartTLS(nil); err != nil {
-			client.Quit()
-			return nil, err
+
+	if !d.TLS {
+		if ok, _ := client.Extension("STARTTLS"); ok {
+			if err = client.StartTLS(nil); err != nil {
+				return
+			}
 		}
 	}
+
 	if ok, _ := client.Extension("AUTH"); ok && d.Account != "" && d.Password != "" {
 		if err = client.Auth2(&smtp.Auth{Identity: "", Username: d.Account, Password: d.Password, Server: d.Server}); err != nil {
 			client.Quit()
@@ -110,5 +118,5 @@ func (d *Dialer) Send(msg ...*Message) error {
 func (d *Dialer) SendMail(ctx context.Context, from string, to []string, msg []byte) error {
 	addr := fmt.Sprintf("%s:%d", d.Server, d.Port)
 	auth := &smtp.Auth{Identity: "", Username: d.Account, Password: d.Password, Server: d.Server}
-	return smtp.SendMail(ctx, addr, auth, from, to, msg)
+	return smtp.SendMail(ctx, addr, d.TLS, auth, from, to, msg)
 }

smtp/smtp.go

@@ -45,6 +45,22 @@ func Dial(ctx context.Context, addr string) (*Client, error) {
 	return NewClient(conn, host)
 }
 
+// DialTLS returns a new Client connected to an SMTP server with TLS connection at addr.
+// The addr must include a port, as in "mail.example.com:smtp".
+func DialTLS(ctx context.Context, addr string) (*Client, error) {
+	host, _, err := net.SplitHostPort(addr)
+	if err != nil {
+		return nil, err
+	}
+
+	d := &tls.Dialer{Config: &tls.Config{ServerName: host}}
+	conn, err := d.DialContext(ctx, "tcp", addr)
+	if err != nil {
+		return nil, err
+	}
+	return NewClient(conn, host)
+}
+
 // NewClient returns a new Client using an existing connection and host as a
 // server name to be used when authenticating.
 func NewClient(conn net.Conn, host string) (*Client, error) {
@@ -163,7 +179,8 @@ func (c *Client) TLSConnectionState() (state tls.ConnectionState, ok bool) {
 	if !ok {
 		return
 	}
-	return tc.ConnectionState(), true
+	state = tc.ConnectionState()
+	return
 }
 
 // Verify checks the validity of an email address on the server.
@@ -371,33 +388,41 @@ func (c *Client) SendMail(from string, to []string, msg []byte) error {
 // fields such as "From", "To", "Subject", and "Cc".  Sending "Bcc"
 // messages is accomplished by including an email address in the to
 // parameter but not including it in the msg headers.
-func SendMail(ctx context.Context, addr string, auth *Auth, from string, to []string, msg []byte) error {
-	if err := validateLine(from); err != nil {
-		return err
+func SendMail(ctx context.Context, addr string, tls bool, auth *Auth, from string, to []string, msg []byte) (err error) {
+	if err = validateLine(from); err != nil {
+		return
 	}
 	for _, recp := range to {
-		if err := validateLine(recp); err != nil {
-			return err
+		if err = validateLine(recp); err != nil {
+			return
 		}
 	}
 
-	c, err := Dial(ctx, addr)
+	var c *Client
+	if tls {
+		c, err = DialTLS(ctx, addr)
+	} else {
+		c, err = Dial(ctx, addr)
+	}
 	if err != nil {
-		return err
+		return
 	}
 	defer c.Quit()
 
-	if ok, _ := c.Extension("STARTTLS"); ok {
-		if err := c.StartTLS(nil); err != nil {
-			return err
+	if !tls {
+		if ok, _ := c.Extension("STARTTLS"); ok {
+			if err = c.StartTLS(nil); err != nil {
+				return
+			}
 		}
 	}
+
 	if auth != nil && c.ext != nil {
 		if _, ok := c.ext["AUTH"]; !ok {
 			return errors.New("smtp: server doesn't support AUTH")
 		}
 		if err = c.Auth2(auth); err != nil {
-			return err
+			return
 		}
 	}