use custom conn

Fix #79, #24

Author: xhit

README.md

@@ -77,6 +77,7 @@ Go Simple Mail supports:
 - Support text/calendar content type body (since v2.11.0)
 - Support add a List-Unsubscribe header (since v2.11.0)
 - Support to add a DKIM signarure (since v2.11.0)
+- Support to send using custom connection, ideal for proxy (since v2.15.0)
 
 ## Documentation
 
@@ -102,7 +103,7 @@ package main
 import (
 	"log"
 
-	"github.com/xhit/go-simple-mail/v2"
+	mail "github.com/xhit/go-simple-mail/v2"
 	"github.com/toorop/go-dkim"
 )
 
@@ -269,6 +270,77 @@ func main() {
 	}
 ```
 
+# Send with custom connection
+
+It's possible to use a custom connection with custom dieler, like a dialer that uses a proxy server, etc...
+
+With this, these servers params are ignored: `Host`, `Port`. You have total control of the connection.
+
+Example using a conn for proxy:
+
+```go
+package main
+
+import (
+	"crypto/tls"
+	"fmt"
+	"log"
+	"net"
+
+	mail "github.com/xhit/go-simple-mail/v2"
+	"golang.org/x/net/proxy"
+)
+
+func main() {
+	server := mail.NewSMTPClient()
+
+	host := "smtp.example.com"
+	port := 587
+	proxyAddr := "proxy.server"
+
+	conn, err := getCustomConnWithProxy(proxyAddr, host, port)
+	if err != nil {
+		log.Fatal(err)
+	}
+
+	server.Username = "[email protected]"
+	server.Password = "examplepass"
+	server.Encryption = mail.EncryptionSTARTTLS
+	server.CustomConn = conn
+
+	smtpClient, err := server.Connect()
+	if err != nil {
+		log.Fatal(err)
+	}
+
+	email := mail.NewMSG()
+
+	err = email.SetFrom("From Example <[email protected]>").AddTo("[email protected]").Send(smtpClient)
+	if err != nil {
+		log.Fatal(err)
+	}
+
+}
+
+func getCustomConnWithProxy(proxyAddr, host string, port int) (net.Conn, error) {
+	dial, err := proxy.SOCKS5("tcp", proxyAddr, nil, proxy.Direct)
+	if err != nil {
+		return nil, err
+	}
+
+	dialer, err := dial.Dial("tcp", fmt.Sprintf("%s:%d", host, port))
+	if err != nil {
+		return nil, err
+	}
+
+	conf := &tls.Config{ServerName: host}
+	conn := tls.Client(dialer, conf)
+
+	return conn, nil
+}
+
+```
+
 ## More examples
 
 See [example/example_test.go](example/example_test.go).

email.go

@@ -52,6 +52,9 @@ type SMTPServer struct {
 	Port           int
 	KeepAlive      bool
 	TLSConfig      *tls.Config
+
+	// use custom dialer
+	CustomConn net.Conn
 }
 
 // SMTPClient represents a SMTP Client for send email
@@ -711,27 +714,30 @@ func (email *Email) SendEnvelopeFrom(from string, client *SMTPClient) error {
 }
 
 // dial connects to the smtp server with the request encryption type
-func dial(host string, port string, encryption Encryption, config *tls.Config) (*smtpClient, error) {
+func dial(customConn net.Conn, host string, port string, encryption Encryption, config *tls.Config) (*smtpClient, error) {
 	var conn net.Conn
 	var err error
+	var c *smtpClient
 
-	address := host + ":" + port
-
-	// do the actual dial
-	switch encryption {
-	// TODO: Remove EncryptionSSL check before launch v3
-	case EncryptionSSL, EncryptionSSLTLS:
-		conn, err = tls.Dial("tcp", address, config)
-	default:
-		conn, err = net.Dial("tcp", address)
-	}
+	if customConn != nil {
+		conn = customConn
+	} else {
+		address := host + ":" + port
+		// do the actual dial
+		switch encryption {
+		// TODO: Remove EncryptionSSL check before launch v3
+		case EncryptionSSL, EncryptionSSLTLS:
+			conn, err = tls.Dial("tcp", address, config)
+		default:
+			conn, err = net.Dial("tcp", address)
+		}
 
-	if err != nil {
-		return nil, errors.New("Mail Error on dialing with encryption type " + encryption.String() + ": " + err.Error())
+		if err != nil {
+			return nil, errors.New("Mail Error on dialing with encryption type " + encryption.String() + ": " + err.Error())
+		}
 	}
 
-	c, err := newClient(conn, host)
-
+	c, err = newClient(conn, host)
 	if err != nil {
 		return nil, fmt.Errorf("Mail Error on smtp dial: %w", err)
 	}
@@ -741,9 +747,9 @@ func dial(host string, port string, encryption Encryption, config *tls.Config) (
 
 // smtpConnect connects to the smtp server and starts TLS and passes auth
 // if necessary
-func smtpConnect(host, port, helo string, encryption Encryption, config *tls.Config) (*smtpClient, error) {
+func smtpConnect(customConn net.Conn, host, port, helo string, encryption Encryption, config *tls.Config) (*smtpClient, error) {
 	// connect to the mail server
-	c, err := dial(host, port, encryption, config)
+	c, err := dial(customConn, host, port, encryption, config)
 
 	if err != nil {
 		return nil, err
@@ -837,7 +843,7 @@ func (server *SMTPServer) Connect() (*SMTPClient, error) {
 	if server.ConnectTimeout != 0 {
 		smtpConnectChannel = make(chan error, 2)
 		go func() {
-			c, err = smtpConnect(server.Host, fmt.Sprintf("%d", server.Port), server.Helo, server.Encryption, tlsConfig)
+			c, err = smtpConnect(server.CustomConn, server.Host, fmt.Sprintf("%d", server.Port), server.Helo, server.Encryption, tlsConfig)
 			// send the result
 			smtpConnectChannel <- err
 		}()
@@ -852,7 +858,7 @@ func (server *SMTPServer) Connect() (*SMTPClient, error) {
 		}
 	} else {
 		// no ConnectTimeout, just fire the connect
-		c, err = smtpConnect(server.Host, fmt.Sprintf("%d", server.Port), server.Helo, server.Encryption, tlsConfig)
+		c, err = smtpConnect(server.CustomConn, server.Host, fmt.Sprintf("%d", server.Port), server.Helo, server.Encryption, tlsConfig)
 		if err != nil {
 			return nil, err
 		}