C# 服务器发送邮件失败实例分析

string host = "smtp.exmail.qq.com";//qq邮箱
 int port = 25;//25 465 587
 string from = "123456@qq.com";
 string to = "456789@qq.com";
 string userName = "123456@qq.com";
 string password = "123456";

 MailMessage message = new MailMessage();
 message.From = new MailAddress(from);
 message.To.Add(new MailAddress(to));
 message.Body = "test body";
 message.Subject = "test subject";
 message.IsBodyHtml = true;
 message.SubjectEncoding = Encoding.UTF8;

 SmtpClient client = new SmtpClient(host, port);
 client.UseDefaultCredentials = true;
 client.Credentials = new NetworkCredential(userName, password);
 client.Send(message);

string host = "smtp.exmail.qq.com";//qq邮箱
 int port = 465;//25 465 587
 string from = "123456@qq.com";
 string to = "456789@qq.com";
 string userName = "123456@qq.com";
 string password = "123456";
 
 var message = new MimeMessage();
 message.From.Add(new MailboxAddress(from));
 message.To.AddRange(new MailboxAddress[] { new MailboxAddress(to) });
 message.Subject = "test subject";
 var entity = new TextPart(TextFormat.Html)
 {
 Text = "test body"
 };
 SmtpClient client = new SmtpClient();
 client.Connect(host, port, port == 465);//465端口是ssl端口
 client.Authenticate(userName, password);
 client.Send(message);
 client.Disconnect(true);