Sample Code: I need functionality for send to your friend…
NetworkCredential loginInfo = new NetworkCredential("admin@gmail.com", "password");
MailAddress to = new MailAddress("mailto@gmail.com");
SmtpClient client = new SmtpClient("smtp.gmail.com");
client.EnableSsl = true;
client.Credentials = loginInfo;
MailAddress from = new MailAddress("from@gmail.com");
MailMessage message = new MailMessage(from, to);
message.Subject = "demo";
message.Body = @"msgBody";
client.Send(message);
Reasion is are you using smtp of Gmail.
it would happend due to security issule like… you are using gmail address and send email as xyz@microsoft.com its may create issue….
thats reasion its not allow by gmail.
it may work with your own domain.