Question

使用gmail smtp出现异常时，我遇到了一个问题。

1）允许安全性较低的应用：打开

2）尝试使用端口587、465、25（相同的例外）

3）尝试禁用SSL（相同的例外）

4）smtp.gmail.com的telnet，用于465、587端口，以及从用于smtp的电子邮件地址直接发送

想法？

public async Task SendEmail(string subject, string message)
{
    MailAddress fromAddress = new MailAddress("user_from@gmail.com");
    MailAddress toAddress = new MailAddress("user_to@gmail.com");

    MailMessage mail = new MailMessage(fromAddress.Address, toAddress.Address);
    mail.Subject = subject;
    mail.Body = message;

    SmtpClient client = new SmtpClient();
    client.Host = "smtp.gmail.com";
    client.Port = 587;
    client.DeliveryMethod = SmtpDeliveryMethod.Network;
    client.EnableSsl = true;
    client.Timeout = 20000;
    client.UseDefaultCredentials = false;
    client.Credentials = new NetworkCredential("user_from@gmail.com", "password");

    try
    {
        client.Send(mail);
    } 
    catch (Exception ex)
    {
        Console.Write(ex.Message);
    }
}

使用端口587的异常：

{System.Net.Mail.SmtpException: The operation has timed out.
    at System.Net.Mail.SmtpClient.Send(MailMessage message)
    at EmailsUtilities.<SendEmail>d__1.MoveNext() in client.Send(mail);

使用端口465的异常：

{System.Net.Mail.SmtpException: Failure sending mail. ---> 
System.IO.IOException: Unable to read data from the transport connection: The 
connection was closed.
   at System.Net.Mail.SmtpReplyReaderFactory.ProcessRead(Byte[] buffer, Int32 
offset, Int32 read, Boolean readLine)
    at System.Net.Mail.SmtpReplyReaderFactory.ReadLines(SmtpReplyReader 
caller, Boolean oneLine)
   at System.Net.Mail.SmtpReplyReaderFactory.ReadLine(SmtpReplyReader caller)
   at System.Net.Mail.SmtpConnection.GetConnection(String host, Int32 port)
   at System.Net.Mail.SmtpTransport.GetConnection(String host, Int32 port)
   at System.Net.Mail.SmtpClient.GetConnection()
   at System.Net.Mail.SmtpClient.Send(MailMessage message)
   --- End of inner exception stack trace ---
  at System.Net.Mail.SmtpClient.Send(MailMessage message)
  at EmailsUtilities.<SendEmail>d__1.MoveNext() in client.Send(mail);

更新：将client.Send(mail)更改为await client.SendMailAsync(mail)后，获得新的异常：

{System.Net.Mail.SmtpException: Syntax error, command 
unrecognized. The server response was: 
   at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
   at 
System.Net.Mail.SmtpConnection.ConnectAndHandshakeAsyncResult.End(IAsyncResult 
 result)
   at System.Net.Mail.SmtpTransport.EndGetConnection(IAsyncResult result)
   at System.Net.Mail.SmtpClient.ConnectCallback(IAsyncResult result)
--- End of stack trace from previous location where exception was thrown ---
   at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
   at 
System.Runtime.CompilerServices.TaskAwaiter
    .HandleNonSuccessAndDebuggerNotificati 
   on(Task task)
       at EmailsUtilities.<SendEmail>d__1.MoveNext() in client.SendMailAsync 
    System.Net.Mail.SmtpException

感谢您的帮助！

Answer 1

最后使用Mail.dll（通过NuGet安装）使电子邮件正常工作。示例：

unsigned int from_hex(char hi_bits, char lo_bits)
{
    return from_hex(hi_bits) * 16 + from_hex(lo_bits);
}

smtp.gmail.com例外，启用发送电子邮件

1 个答案: