说明：本来打算用sina的，(smtp.sina.com) ，但经过测试，感觉这个非常不稳定，所以改用GMail的smtp服务，感觉非常稳定、快速。记录下来，方便后来者！

Method 1

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// using System.Net.Mail;

Mailmessageage message = new Mailmessageage();

message.From = new MailAddress("User@gmail.com", "Your DisplayName");

message.To.Add(new MailAddress("To@gmail.com")); // the email you want to send email to

message.Subject = "A test email"

message.IsBodyHtml = true;

message.BodyEncoding = System.Text.Encoding.UTF8;

message.Body = "this is just a simple test!<br> Jack"

message.Priority = MailPriority.High;

SmtpClient client = new SmtpClient("smtp.gmail.com", 587); // 587;//Gmail使用的端口

client.Credentials = new System.Net.NetworkCredential("User@gmail.com", "*****"); // Your user name & password

client.EnableSsl = true; //经过ssl加密

object userState = message;

try

{

client.Send(message);

Response.Write("邮件发送到" + message.To.ToString() + "<br>");

}

catch (Exception ee)

{

Response.Write(ee.messageage + "<br>" + ee.InnerException.messageage);

}

Method 2

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//

// using System.Net.Mail;

MailMessage message = new MailMessage();

message.From = new MailAddress("User@gmail.com");

message.To.Add(new MailAddress("to@gmail.com"));

message.Subject = "This is my subject"

message.Body = "This is the content"

SmtpClient client = new SmtpClient();

client.EnableSsl = true;

try

{

client.Send(message);

Response.Write("邮件发送到" + message.To.ToString() + "<br>");

}

catch (Exception ee)

{

Response.Write(ee.Message );

}

//In web.config

<system.net>

<mailSettings>

<smtp from="from@gmail.com">

<network host="smtp.gmail.com" port="587" userName="User@gmail.com" password="your pwd" />

<!-- if has 'defaultCredentials="true"' , using Gmail can not send success -->

</smtp>

</mailSettings>

</system.net>