diff --git a/.gitignore b/.gitignore
new file mode 100644
index 0000000..b9c26cf
--- /dev/null
+++ b/.gitignore
@@ -0,0 +1 @@
+/go.work
diff --git a/go.mod b/go.mod
new file mode 100644
index 0000000..8675b04
--- /dev/null
+++ b/go.mod
@@ -0,0 +1,8 @@
+module github.com/helays/gomail/v2
+
+
+require (
+	golang.org/x/net v0.44.0
+	gopkg.in/alexcesaro/quotedprintable.v3 v3.0.0-20150716171945-2caba252f4dc
+	gopkg.in/gomail.v2 v2.0.0-20160411212932-81ebce5c23df
+)
diff --git a/smtp.go b/smtp.go
index 2aa49c8..6729fa2 100644
--- a/smtp.go
+++ b/smtp.go
@@ -8,6 +8,8 @@ import (
 	"net/smtp"
 	"strings"
 	"time"
+
+	"golang.org/x/net/proxy"
 )
 
 // A Dialer is a dialer to an SMTP server.
@@ -33,6 +35,7 @@ type Dialer struct {
 	// LocalName is the hostname sent to the SMTP server with the HELO command.
 	// By default, "localhost" is sent.
 	LocalName string
+	Dialer    proxy.Dialer
 }
 
 // NewDialer returns a new SMTP Dialer. The given parameters are used to connect
@@ -58,7 +61,16 @@ func NewPlainDialer(host string, port int, username, password string) *Dialer {
 // Dial dials and authenticates to an SMTP server. The returned SendCloser
 // should be closed when done using it.
 func (d *Dialer) Dial() (SendCloser, error) {
-	conn, err := netDialTimeout("tcp", addr(d.Host, d.Port), 10*time.Second)
+	var (
+		conn net.Conn
+		err  error
+	)
+	if d.Dialer != nil {
+		conn, err = d.Dialer.Dial("tcp", addr(d.Host, d.Port))
+	} else {
+		conn, err = netDialTimeout("tcp", addr(d.Host, d.Port), 10*time.Second)
+	}
+
 	if err != nil {
 		return nil, err
 	}
@@ -80,7 +92,7 @@ func (d *Dialer) Dial() (SendCloser, error) {
 
 	if !d.SSL {
 		if ok, _ := c.Extension("STARTTLS"); ok {
-			if err := c.StartTLS(d.tlsConfig()); err != nil {
+			if err = c.StartTLS(d.tlsConfig()); err != nil {
 				c.Close()
 				return nil, err
 			}