The server response was: 5.5.1 authentication required in Gmail

Introduction 

          Today i came  across an forum post saying  cant able to send a mail to his domain that he purchased but able to send mail to gmail to gmail.The actual is gmail wants the clients to be secure even throw we set EnableSsl = true;

simply it wont work.

       

           To fix the issue add the RemoteCertificateValidationCallback then it will work fine.

1. public class Program  
2.     {  
3.         static void Main(string[] args)  
4.         {  
5.             string senderID = "xxx@gmail.com";  
6.             string senderPassword = "xxxx";  
7.             RemoteCertificateValidationCallback orgCallback = ServicePointManager.ServerCertificateValidationCallback;  
8.             string body = "Test";  
9.             try  
10.             {  
11.                 ServicePointManager.ServerCertificateValidationCallback = new RemoteCertificateValidationCallback(OnValidateCertificate);  
12.                 ServicePointManager.Expect100Continue = true;  
13.                 MailMessage mail = new MailMessage();  
14.                 mail.To.Add("danish.habib@plan-international.org");  
15.                 mail.From = new MailAddress(senderID);  
16.                 mail.Subject = "My Test Email!";  
17.                 mail.Body = body;  
18.                 mail.IsBodyHtml = true;  
19.                 SmtpClient smtp = new SmtpClient();  
20.                 smtp.Host = "smtp.gmail.com";  
21.                 smtp.Credentials = new System.Net.NetworkCredential(senderID, senderPassword);  
22.                 smtp.Port = 587;  
23.                 smtp.EnableSsl = true;  
24.                 smtp.Send(mail);  
25.                 Console.WriteLine("Email Sent Successfully");  
26.             }  
27.             catch (Exception ex)  
28.             {  
29.                 Console.WriteLine(ex.Message);  
30.             }  
31.             finally  
32.             {  
33.                 ServicePointManager.ServerCertificateValidationCallback = orgCallback;  
34.             }  
35.         }  
36.   
37.         private static bool OnValidateCertificate(object sender, X509Certificate certificate, X509Chain chain, SslPolicyErrors sslPolicyErrors)  
38.         {  
39.             return true;  
40.         }  
41.     }