邮件发送失败。无法连接到远程服务器。套接字操作

Posted 2023-03-15

【中文标题】邮件发送失败。无法连接到远程服务器。套接字操作

【英文标题】：Failure Sending Mail. Unable to connect to remote server. A socket operation

【发布时间】：2015-06-09 02:11:50

【问题描述】：

所以我试图通过 VB.net 代码发送电子邮件，但我不断收到此错误。我禁用了防火墙，当它没有从文本框中获取文本时，我可以成功发送电子邮件。我知道当我发送一封正文为 1 行的电子邮件时，我的设置正确。

Private Sub SendMessage(ByVal SmtpHost As String, ByVal SmtpPort As Integer, ByVal ssl As Boolean, ByVal SmtpUsername As String, ByVal SmtpPassword As String, ByVal mail_from As String, ByVal display_name As String, ByVal Send_To As String, ByVal subject As String, ByVal Body As String, Optional ByVal Attachments As String() = Nothing)
        Using smtp As New SmtpClient
            smtp.Host = SmtpHost
            smtp.Port = SmtpPort
            smtp.UseDefaultCredentials = False
            smtp.Credentials = New Net.NetworkCredential(SmtpUsername, SmtpPassword)
            smtp.EnableSsl = ssl

            Dim message As New MailMessage()
            Try
                message.From = New MailAddress(mail_from, display_name, System.Text.Encoding.UTF8)
                message.To.Add(Send_To)
                message.Subject = subject
                message.Body = Body
                If Attachments IsNot Nothing Then
                    For Each attachment As String In Attachments
                        message.Attachments.Add(New Attachment(attachment))
                    Next
                End If
                message.ReplyToList.Add(New MailAddress(mail_from))

                smtp.Send(message)
            Catch ex As Exception
                Debug.WriteLine(ex)
            End Try
        End Using

错误：

System.Net.Mail.SmtpException: Failure sending mail. ---> System.Net.WebException: Unable to connect to the remote server ---> System.Net.Sockets.SocketException: A socket operation was attempted to an unreachable network 0.0.0.1:465
   at System.Net.Sockets.Socket.DoConnect(EndPoint endPointSnapshot, SocketAddress socketAddress)
   at System.Net.ServicePoint.ConnectSocketInternal(Boolean connectFailure, Socket s4, Socket s6, Socket& socket, IPAddress& address, ConnectSocketState state, IAsyncResult asyncResult, Exception& exception)
   --- End of inner exception stack trace ---
   at System.Net.ServicePoint.GetConnection(PooledStream PooledStream, Object owner, Boolean async, IPAddress& address, Socket& abortSocket, Socket& abortSocket6)
   at System.Net.PooledStream.Activate(Object owningObject, Boolean async, GeneralAsyncDelegate asyncCallback)
   at System.Net.ConnectionPool.GetConnection(Object owningObject, GeneralAsyncDelegate asyncCallback, Int32 creationTimeout)
   at System.Net.Mail.SmtpConnection.GetConnection(ServicePoint servicePoint)
   at System.Net.Mail.SmtpClient.Send(MailMessage message)
   --- End of inner exception stack trace ---
   at System.Net.Mail.SmtpClient.Send(MailMessage message)
   at EmailSender.Form1.Timer2_Tick(Object sender, EventArgs e)

【问题讨论】：

你没有提到你得到的错误......另外请澄清这一点，“但是当我在文本框中输入时，它不仅仅是一行，可能是这样吗？我怎样才能做到这一点'将发送多行电子邮件？这没有意义......

我更改了 Smtp 电子邮件代码，但仍然遇到同样的问题，我用错误更新了问题。

你有计时器吗？ ...

是的，我有一个计时器在做这个，看看它是否能正常工作......但是它甚至没有一次与计时器一起工作。

【参考方案1】：

您的代码可能没有任何错误。但是，如果您的邮件帐户配置不正确，则会发生这种特定的“发送邮件失败”。您必须允许访问第三方或外部应用程序才能使用您邮件的 SMTP 服务。您可以在邮件设置中更改它。

改变它并尝试。这可能行得通。

【讨论】：

我认为这也是原因，因为我记得过去必须这样做。我会四处寻找，然后回复发生的情况。

是否允许访问不太安全的应用程序？如果是这样，我已经打开了。

没有。你不必那样做。只允许 SMTP 访问。您使用哪种服务发送邮件？我的意思是像 gmail 或任何其他？

我正在使用 Gmail，是的，先生

好吧，我发现端口 25 和 465 不起作用，因为它无法通过 telnet。所以代码运行良好，它只是我的电脑。

【参考方案2】：

Try
Dim mMailMessage As MailMessage = New System.Net.Mail.MailMessage()
Dim fromEmail As String = "<sender_mail_ID"
Dim fromPW As String = "<sender_password>"
Dim toEmail As String = "<Receiver_mail_ID>"
mMailMessage.From = New MailAddress(fromEmail)
mMailMessage.[To].Add(toEmail)
mMailMessage.Subject = "<Subject goes here>"
mMailMessage.Body = "<Message AKA Body goes here>"
mMailMessage.DeliveryNotificationOptions = DeliveryNotificationOptions.OnFailure

Dim smtpClient As New SmtpClient("smtp.gmail.com", 587)
smtpClient.EnableSsl = True
smtpClient.DeliveryMethod = SmtpDeliveryMethod.Network
smtpClient.UseDefaultCredentials = False
smtpClient.Credentials = New NetworkCredential(fromEmail, fromPW)

smtpClient.Send(mMailMessage.From.ToString(), mMailMessage.[To].ToString(), mMailMessage.Subject, mMailMessage.Body)

Catch ex As Exception

End Try

别忘了使用：

Imports System.Net.Mail
Imports System.Net

【参考方案3】：

我的 2 美分。在我的情况下，我把所有东西都布置得很完美，什么让我没有意识到我在后台运行了 privateinternetaccess 应用程序，这阻止了每次连接到服务器的尝试。不酷:(