[c#] _ Config to Send mail EWS in server

See more:

server

EWS

server-control

Hi every body,
Please help me why i build a project to send mail, when i run at my computer that ok, So i run on another server have a error "The remote server returned an error: (401) Unauthorized.". I dont know that is my code error or server config my account.
This is my code

ServicePointManager.ServerCertificateValidationCallback = delegate { return true; };
              ExchangeService service = new ExchangeService(Microsoft.Exchange.WebServices.Data.ExchangeVersion.Exchange2007_SP1);

              service.Credentials = new WebCredentials(@"domain\myuser", "mypass");

              service.Url = new System.Uri("https://mail.domain.com/EWS/Exchange.asmx");

              EmailMessage email = new EmailMessage(service);
              email.ToRecipients.Add(MrK, mrk@domain.com);
              email.Subject = "Test From Smart's Server";
              email.Body = new MessageBody(string.Format(_body_mail, prnumber, "hey you", purposeofpur));
              email.Send();

Thank you so much