Can't access to gmail using the build

Hi everyone. I need to send an email using the game and I've this issue.

When I try the game in the editor it sends the mail correctly.

When I build the game and I try to send the email using the .exe file it raises this:

Platform assembly: D:\DropBox Storage\Dropbox\Project\Exec\Exec PC\Updated version\OSR_Data\Managed\Mono.Security.dll (this message is harmless) SmtpException: 530-5.5.1 Authentication Required. Learn more at

530 5.5.1 http://support.google.com/mail/bin/answer.py?answer=14257 l10sm4506847wif.20 - gsmtp

at System.Net.Mail.SmtpClient.SendCore (System.Net.Mail.MailMessage message) [0x00000] in :0

at System.Net.Mail.SmtpClient.SendInternal (System.Net.Mail.MailMessage message) [0x00000] in :0

at System.Net.Mail.SmtpClient.Send (System.Net.Mail.MailMessage message) [0x00000] in :0

The Code I'm using is the following:

 static public void mono_gmail (string receiver, string subject, string body)
     {
         MailMessage mail = new MailMessage();

         //mail content here
         mail.From = new MailAddress(sampleemail@gmail.com, "Name");
         mail.To.Add(receiver);
         mail.Subject = subject;
         mail.Body = body;

         //attaching a file here
         System.Net.Mail.Attachment data;
         data = new System.Net.Mail.Attachment("filePathhere");
         mail.Attachments.Add(data);
 
         SmtpClient smtpServer = new SmtpClient(senderSmtp);
         smtpServer.Port = 587;
 
         smtpServer.Credentials = new System.Net.NetworkCredential(senderEmail, senderPassword) as ICredentialsByHost;
            smtpServer.EnableSsl = true;
         ServicePointManager.ServerCertificateValidationCallback = 
         delegate(object s, X509Certificate certificate, X509Chain chain, SslPolicyErrors sslPolicyErrors) 
         { return true; };
         
         smtpServer.Send(mail);
         Debug.Log("success");
         
     }