hey , i tried to make the email sender in c# using visual studio 2015 but i got an error , while i press send email it gives me error your credentials are incorrect but i am using a correct email this is the code : 
private void button1_Click(object sender, EventArgs e) 

try 

if (!textBox4.Text.Contains("@gmail.com")) 

MessageBox.Show("Please Provide a gmail address", "Error", MessageBoxButtons.OK, MessageBoxIcon.Error); 
return; 

button1.Enabled = false; 
MailMessage message = new MailMessage(); 
message.From = new MailAddress(textBox4.Text); 
message.Subject = textBox2.Text; 
message.Body = textBox3.Text; 
foreach (string s in textBox1.Text.Split(';')) 
message.To.Add(s); 
SmtpClient client = new SmtpClient(); 
client.Credentials = new NetworkCredential(textBox4.Text, textBox5.Text); 
client.Host = "smtp.gmail.com"; 
client.Port = 587; 
client.EnableSsl = true; 
client.Send(message); 

catch { MessageBox.Show("There was an error sending the massage.\r\nPlease Make Sure That Your Credentials are Correct\r\nAnd that you have an internet conection.", "Error", MessageBoxButtons.OK, MessageBoxIcon.Error); } 
finally { button1.Enabled = true; 

}