Send mail from Unity5

Hi everyone, im trying to send email from C#, Unity5, but my unity always frezee, when i call send mail.

 using UnityEngine;
 using System.Collections;
 using System;
 using System.Net;
 using System.Net.Mail;
 using System.Net.Security;
 using System.Security.Cryptography.X509Certificates;
 
 public class SentEmail : MonoBehaviour {
 
     public string sender = "mail@gmail.com";
     public string receiver = "mail@gmail.com";
     public string smtpPassword = "password";
     public string smtpHost = "smtp.gmail.com";
 
     public void sentMail()
     {
         try
         {
             using (var mail = new MailMessage
             {
                 From = new MailAddress(sender),
                 Subject = "test subject",
                 Body = "Hello there!"
             })
             {
                 mail.To.Add(receiver);
 
                 var smtpServer = new SmtpClient(smtpHost)
                 {
                     Port = 25,
                     Credentials = (ICredentialsByHost)new NetworkCredential(sender, smtpPassword)
                 };
                 ServicePointManager.ServerCertificateValidationCallback = delegate { return true; };
                 smtpServer.EnableSsl = true;
                 Debug.Log("HERE");
                 smtpServer.Send(mail);
                 Debug.Log("SUCCESFUL");
             }
 
         }
         catch (Exception e)
         {
             Debug.Log(e.GetBaseException());
         }
 
     }
 }
 

Debug with "HERE" works.. but others nothing, Can u help me?