问当通过C# SmtpClient发送电子邮件时，为什么收件人会看到用户名而不是发送者或电子邮件？

EN

MailMessage mail = new MailMessage("from@email.com", "to@email.com");
mail.Subject = "subject";
mail.Body = "body";
mail.IsBodyHtml = true;
mail.Sender = "from@email.com";

SmtpClient client = new SmtpClient();
client.Port = 587;
client.DeliveryMethod = SmtpDeliveryMethod.Network;
client.UseDefaultCredentials = false;
client.Host = smpt.gmail.com;
client.Credentials = new NetworkCredential("username@gmail.com", "password");
client.EnableSsl = true;
client.Send(mail);