C# SMTP 电子邮件发送代码对于 Yahoo Mail 失败但对于其他服务器工作正常，任何人都可以帮忙吗？

Question

我正在使用此代码通过雅虎 SMTP 服务器发送 SMTP 电子邮件，它用于我正在编写的个人项目。

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

SmtpClient theClient = new SmtpClient("smtp.mail.yahoo.com", 465);
theClient.UseDefaultCredentials = false;
theClient.Credentials = new NetworkCredential("username", "password");
theClient.EnableSsl = true;

MailMessage theMessage = new MailMessage("username@yahoo.com", 
                                         "to.someone@gmail.com");

theMessage.Subject = "Dave test from C# subject";
theMessage.Body = "Dave test from C# body";

theClient.Send(theMessage);

这都是发送 SMTP 电子邮件的非常标准的代码，但是......服务器似乎抛出错误。它强行终止连接。如果我使用其他 SMTP 服务器(如 Gmail、Windows Live 或各种其他 ISP Smtp 服务器)，则不会发生这种情况。

这是异常和堆栈跟踪:

System.IO.IOException: Unable to read data from the transport connection: An existing connection was forcibly closed by the remote host.
at System.Net.Mail.SmtpClient.Send(MailMessage message)
at ConsoleApplication1.Program.Main(String[] args) in E:\dev\ARCSoftware.FTPProcessor\ConsoleApplication1\Program.cs:line 28

我知道问题不是环境问题，因为我可以使用 Outlook Express 将这些确切设置发送到同一台服务器。请问需要发证书什么的吗？

如果您或您认识的任何人对此有任何想法，我将非常感谢您的帮助。

Answer 1

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

public partial class MainWindow : Window
{
    public MainWindow()
    {
        InitializeComponent();
    }

    private void btn_Send_Click(object sender, RoutedEventArgs e)
    {
        MailMessage oMail = new MailMessage(new MailAddress("username@yahoo.com"), new MailAddress("username@yahoo.com"));
        SmtpClient oSmtp = new SmtpClient();
        oSmtp.Host = "smtp.mail.yahoo.com";
        oSmtp.Credentials = new NetworkCredential("username", "password");
        oSmtp.EnableSsl = false;
        oSmtp.Port = 587;
        oSmtp.Send(oMail);
    }
}