發送電子郵件時出錯

我想用c＃發送電子郵件以下是我的代碼。發送電子郵件時出錯

try 
{ 
    System.Net.Mail.MailMessage msg = new System.Net.Mail.MailMessage(); 
    msg.From = new MailAddress("[email protected]"); 
    msg.To.Add("[email protected]");//Text Box for To Address 
    msg.Subject = "Testinng subject"; //Text Box for subject 
    msg.IsBodyHtml = true; 
    msg.Body = "testing comment is here..";//Text Box for body 
    msg.Priority = MailPriority.High; 

    SmtpClient client = new SmtpClient("smtp.gmail.com", 587); 
    client.UseDefaultCredentials = false; 
    client.Credentials = new NetworkCredential("[email protected]", ""); 
    client.Port = 587; 
    client.Host = "smtp.gmail.com"; 
    client.EnableSsl = true; 

    object userstate = msg;  
    client.Send(msg); 
} 
catch (Exception ex) 
{ 
    throw ex; 
}

捐贈以下異常 enter image description here