client.go

@@ -170,9 +170,6 @@ type (
 		// requestDSN indicates wether we want to request DSN (Delivery Status Notifications).
 		requestDSN bool
 
-		// sendMutex is used to synchronize access to shared resources during the dial and send methods.
-		sendMutex sync.Mutex
-
 		// smtpAuth is the authentication type that is used to authenticate the user with SMTP server. It
 		// satisfies the smtp.Auth interface.
 		//
@@ -1061,8 +1058,6 @@ func (c *Client) DialAndSend(messages ...*Msg) error {
 //   - An error if the connection fails, if sending the messages fails, or if closing the
 //     connection fails; otherwise, returns nil.
 func (c *Client) DialAndSendWithContext(ctx context.Context, messages ...*Msg) error {
-	c.sendMutex.Lock()
-	defer c.sendMutex.Unlock()
 	if err := c.DialWithContext(ctx); err != nil {
 		return fmt.Errorf("dial failed: %w", err)
 	}

client_test.go

@@ -2297,45 +2297,6 @@ func TestClient_DialAndSendWithContext(t *testing.T) {
 			t.Errorf("client was supposed to fail on dial")
 		}
 	})
-	t.Run("concurrent sending via DialAndSendWithContext", func(t *testing.T) {
-		ctx, cancel := context.WithCancel(context.Background())
-		defer cancel()
-		PortAdder.Add(1)
-		serverPort := int(TestServerPortBase + PortAdder.Load())
-		featureSet := "250-8BITMIME\r\n250-DSN\r\n250 SMTPUTF8"
-		go func() {
-			if err := simpleSMTPServer(ctx, t, &serverProps{
-				FeatureSet: featureSet,
-				ListenPort: serverPort,
-			}); err != nil {
-				t.Errorf("failed to start test server: %s", err)
-				return
-			}
-		}()
-		time.Sleep(time.Millisecond * 30)
-
-		client, err := NewClient(DefaultHost, WithPort(serverPort), WithTLSPolicy(NoTLS))
-		if err != nil {
-			t.Fatalf("failed to create new client: %s", err)
-		}
-
-		wg := sync.WaitGroup{}
-		for i := 0; i < 50; i++ {
-			wg.Add(1)
-			go func() {
-				defer wg.Done()
-				msg := testMessage(t)
-				msg.SetMessageIDWithValue("this.is.a.message.id")
-
-				ctxDial, cancelDial := context.WithTimeout(ctx, time.Minute)
-				defer cancelDial()
-				if goroutineErr := client.DialAndSendWithContext(ctxDial, msg); goroutineErr != nil {
-					t.Errorf("failed to dial and send message: %s", goroutineErr)
-				}
-			}()
-		}
-		wg.Wait()
-	})
 }
 
 func TestClient_auth(t *testing.T) {