In previous section, I introduced how to use event handler to monitor the progress. In this section, I will introduce how to send email in asynchronous mode in VB.NET.
In synchronous mode, once SendMail method is called, it returns to application after the method is complete. Therefore, if the runtime (it depends on the networking connection and the email size) is long, your application cannot do anything before this method ends, which results “my application is blocked or halted”. In contrast, in asynchronous mode, as BeginSendMail method works in background, this methods return to application immediately no matter the running method is complete or not.
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.
The following example codes demonstrate how to send email asynchronously in VB.NET.
To get the full sample projects, please refer to Samples section.
Imports EASendMail 'Add EASendMail namespace Module Module1 Sub Main() Try Dim oMail As New SmtpMail("TryIt") ' Set sender email address, please change it to yours oMail.From = "firstname.lastname@example.org" ' Set recipient email address, please change it to yours oMail.To = "email@example.com" ' Set email subject oMail.Subject = "test asynchronous email from VB.NET" ' Set email body oMail.TextBody = "this is a test email sent from VB.NET with asynchronous mode" ' Your SMTP server address Dim oServer As New SmtpServer("smtp.emailarchitect.net") ' User and password for ESMTP authentication oServer.User = "firstname.lastname@example.org" 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 Console.WriteLine("start to send email in asynchronous mode ...") Dim oSmtp As New SmtpClient() Dim oResult As SmtpClientAsyncResult = oSmtp.BeginSendMail( _ oServer, oMail, Nothing, Nothing) ' Wait for the email sending... Do While (Not oResult.IsCompleted) Console.WriteLine("waiting..., you can do other thing!") oResult.AsyncWaitHandle.WaitOne(50, False) Loop oSmtp.EndSendMail(oResult) Catch ep As Exception Console.WriteLine("failed to send email with the following error:") Console.WriteLine(ep.Message) End Try End Sub End Module
At next section I will introduce how to send mass email with multiple threads in VB.
If you have any comments or questions about above example codes, please click here to add your comments.