Send Email with Multiple Threads(Mass Mail) in VB.NET¶

Imports EASendMail 'Add EASendMail namespace

Module Module1

    Sub Main()

       Dim arRcpt() As String = {"test1@adminsystem.com", _
            "test2@adminsystem.com", _
            "test3@adminsystem.com"}

        Dim nRcpt As Integer = arRcpt.Length
        Dim arMail(nRcpt - 1) As SmtpMail
        Dim arSmtp(nRcpt - 1) As SmtpClient
        Dim arResult(nRcpt - 1) As SmtpClientAsyncResult

        For i As Integer = 0 To nRcpt - 1
            arMail(i) = New SmtpMail("TryIt")
            arSmtp(i) = New SmtpClient()
        Next

        For i As Integer = 0 To nRcpt - 1
            Dim oMail As SmtpMail = arMail(i)

            ' Set sender email address
            oMail.From = "sender@emailarchitect.net"
            ' Set recipient email address
            oMail.To = arRcpt(i)

            ' Set email subject
            oMail.Subject = "mass email test from vb.net"
            ' Set email body
            oMail.TextBody = "test from VB, this email is sent to " + arRcpt(i)

            ' Your SMTP server address
            Dim oServer As New SmtpServer("smtp.emailarchitect.net")

            ' User and password for ESMTP authentication
            oServer.User = "test@emailarchitect.net"
            oServer.Password = "testpassword"

            ' Most mordern SMTP servers require SSL/TLS connection now.
            ' ConnectTryTLS means if server supports SSL/TLS, SSL/TLS will be used automatically.
            oServer.ConnectType = SmtpConnectType.ConnectTryTLS

            ' If your SMTP server uses 587 port
            ' oServer.Port = 587

            ' If your SMTP server requires SSL/TLS connection on 25/587/465 port
            ' oServer.Port = 25 ' 25 or 587 or 465
            ' oServer.ConnectType = SmtpConnectType.ConnectSSLAuto

            Dim oSmtp As SmtpClient = arSmtp(i)

            ' Submit email to BeginSendMail method and return
            ' to process another email
            arResult(i) = oSmtp.BeginSendMail(oServer, oMail, Nothing, Nothing)
            Console.WriteLine(String.Format("Start to send email to {0} ...", _
                arRcpt(i)))
        Next

        ' all emails were sent by BeginSendMail Method
        ' now get result by EndSendMail method
        Dim nSent As Integer = 0
        Do While (nSent < nRcpt)
            For i As Integer = 0 To nRcpt - 1
                ' this email is finished
                If (arResult(i) Is Nothing) Then
                    Continue For
                End If
                ' wait for specified email ...
                If (Not arResult(i).AsyncWaitHandle.WaitOne(10, False)) Then
                    Continue For
                End If
                Try
                    ' this email is finished, using EndSendMail to get result
                    arSmtp(i).EndSendMail(arResult(i))
                    Console.WriteLine(String.Format("Send email to {0} successfully", _
                        arRcpt(i)))
                Catch ep As Exception
                    Console.WriteLine( _
                           String.Format("Failed to send email to {0} with error {1}: ", _
                           arRcpt(i), ep.Message))
                End Try
                ' Set this email result to null, then it won't be processed again
                arResult(i) = Nothing
                nSent += 1
            Next
        Loop

    End Sub

End Module