终于开始工作了:)

using System.Net.Mail;
using System.Text;

...

// Command line argument must the the SMTP host.
SmtpClient client = new SmtpClient();
client.Port = 587;
client.Host = "smtp.gmail.com";
client.EnableSsl = true;
client.Timeout = 10000;
client.DeliveryMethod = SmtpDeliveryMethod.Network;
client.UseDefaultCredentials = false;
client.Credentials = new System.Net.NetworkCredential("user@gmail.com","password");

MailMessage mm = new MailMessage("donotreply@domain.example", "sendtomyemail@domain.example", "test", "test");
mm.BodyEncoding = UTF8Encoding.UTF8;
mm.DeliveryNotificationOptions = DeliveryNotificationOptions.OnFailure;

client.Send(mm);

抱歉之前拼写不太好

使用发件人和收件人的电子邮件地址初始化MailMessage。应该是这样的

string from = "codeforwin@gmail.com";  //Senders email   
string to = "reciever@gmail.com";  //Receiver's email  
MailMessage msg = new MailMessage(from, to); 

阅读如何用c#发送电子邮件的完整代码片段

这也可以…

string your_id = "your_id@gmail.com";
string your_password = "password";
try
{
   SmtpClient client = new SmtpClient
   {
     Host = "smtp.gmail.com",
     Port = 587,
     EnableSsl = true,
     DeliveryMethod = SmtpDeliveryMethod.Network,
     Credentials = new System.Net.NetworkCredential(your_id, your_password),
     Timeout = 10000,
   };
   MailMessage mm = new MailMessage(your_iD, "recepient@gmail.com", "subject", "body");
   client.Send(mm);
   Console.WriteLine("Email Sent");
 }
 catch (Exception e)
 {
   Console.WriteLine("Could not end email\n\n"+e.ToString());
 }

首先去https://myaccount.google.com/lesssecureapps，并允许不太安全的应用程序为真。

然后使用下面的代码。这下面的代码只会工作，如果你的电子邮件地址是从gmail。

static void SendEmail()
    {
        string mailBodyhtml =
            "<p>some text here</p>";
        var msg = new MailMessage("from@gmail.com", "to1@gmail.com", "Hello", mailBodyhtml);
        msg.To.Add("to2@gmail.com");
        msg.IsBodyHtml = true;
        var smtpClient = new SmtpClient("smtp.gmail.com", 587); //**if your from email address is "from@hotmail.com" then host should be "smtp.hotmail.com"**
        smtpClient.UseDefaultCredentials = true;
        smtpClient.Credentials = new NetworkCredential("from@gmail.com", "password");
        smtpClient.EnableSsl = true;
        smtpClient.Send(msg);
        Console.WriteLine("Email Sent Successfully");
    }

到2017年3月，这对我来说是有效的。 从上面的解决方案开始:“终于开始工作了:)”，一开始并没有工作。

SmtpClient client = new SmtpClient();
client.Port =  587;
client.Host = "smtp.gmail.com";
client.EnableSsl = true;
client.Timeout = 10000;
client.DeliveryMethod = SmtpDeliveryMethod.Network;
client.UseDefaultCredentials = false;
client.Credentials = new System.Net.NetworkCredential("<me>@gmail.com", "<my pw>");
MailMessage mm = new MailMessage(from_addr_text, to_addr_text, msg_subject, msg_body);
mm.BodyEncoding = UTF8Encoding.UTF8;
mm.DeliveryNotificationOptions = DeliveryNotificationOptions.OnFailure;

client.Send(mm);

 //Hope you find it useful, it contain too many things

    string smtpAddress = "smtp.xyz.com";
    int portNumber = 587;
    bool enableSSL = true;
    string m_userName = "support@xyz.com";
    string m_UserpassWord = "56436578";

    public void SendEmail(Customer _customers)
    {
        string emailID = gghdgfh@gmail.com;
        string userName = DemoUser;

        string emailFrom = "qwerty@gmail.com";
        string password = "qwerty";
        string emailTo = emailID;

        // Here you can put subject of the mail
        string subject = "Registration";
        // Body of the mail
        string body = "<div style='border: medium solid grey; width: 500px; height: 266px;font-family: arial,sans-serif; font-size: 17px;'>";
        body += "<h3 style='background-color: blueviolet; margin-top:0px;'>Aspen Reporting Tool</h3>";
        body += "<br />";
        body += "Dear " + userName + ",";
        body += "<br />";
        body += "<p>";
        body += "Thank you for registering </p>";            
        body += "<p><a href='"+ sURL +"'>Click Here</a>To finalize the registration process</p>";
        body += " <br />";
        body += "Thanks,";
        body += "<br />";
        body += "<b>The Team</b>";
        body += "</div>";
       // this is done using  using System.Net.Mail; & using System.Net; 
        using (MailMessage mail = new MailMessage())
        {
            mail.From = new MailAddress(emailFrom);
            mail.To.Add(emailTo);
            mail.Subject = subject;
            mail.Body = body;
            mail.IsBodyHtml = true;
            // Can set to false, if you are sending pure text.

            using (SmtpClient smtp = new SmtpClient(smtpAddress, portNumber))
            {
                smtp.Credentials = new NetworkCredential(emailFrom, password);
                smtp.EnableSsl = enableSSL;
                smtp.Send(mail);
            }
        }
    }