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

In previous section, I introduced how to use asynchronous mode. In this section, I will introduce how to send mass emails with multiple threads in VB.NET.


Based on asynchronous mode, you can create multiple SmtpClient instances in your application and send email in multiple threads. Here is a simple sample demonstrates how to use asynchronous mode to send email in multiple threads.


Remarks: All of samples in this section are based on first section: Send email in a simple VB.NET project. To compile and run the following example codes successfully, please click here to learn how to create the test project and add reference of EASendMail to your project.

[VB.NET - Send Mass Emails with Multiple Threads - Example]

The following example codes demonstrate how to send mass email with multiple threads in VB.NET.


To get the full sample projects, please refer to Samples section.

Imports EASendMail 'Add EASendMail namespace

Module Module1

    Sub Main()

       Dim arRcpt() As String = {"", _
            "", _

        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()

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

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

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

            ' Your SMTP server address
            Dim oServer As New SmtpServer("")

            ' User and password for ESMTP authentication
            oServer.User = ""
            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} ...", _

        ' 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
                    ' this email is finished, using EndSendMail to get result
                    Console.WriteLine(String.Format("Send email to {0} successfully", _
                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

    End Sub

End Module

I strongly suggest that you have a look at Mass sample project, it uses a thread pool to send mass emails and support throttling control.


To get the full sample projects, please refer to Samples section.

Next Section

At next section I will introduce how to send email using EASendMail Service Queue in ASP.NET/VB.



If you have any comments or questions about above example codes, please click here to add your comments.