No difference with ASP.NET asynchronous email

Hi, I was making some upgrades to my code for emails to be sent asynchronously however I notice there is no difference in the delay after the user click s the send button.

This is the normal code

  Dim mail As New MailMessage()
        mail.From = New MailAddress(Label9.Text)
        mail.To.Add(Label9.Text)

        'set the content
        mail.Subject = "Normal"

        mail.IsBodyHtml = True

        'send the message
        Dim smtp As New SmtpClient("smtpserver") '
        smtp.Send(mail)

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This is the new asynchronous method;

 Dim mailMessage As New System.Net.Mail.MailMessage

        mailMessage.From = New MailAddress(Label9.Text)
        mailMessage.To.Add("itsupport@seabrookcrisps.com")

        mailMessage.Subject = "Async Email"

        mailMessage.IsBodyHtml = True
        mailMessage.Body = "Test"

        Dim smtpClient As New SmtpClient()
        Dim userState As Object = mailMessage

        'Attach event handler for async callback
        AddHandler smtpClient.SendCompleted, AddressOf SmtpClient_OnCompleted

        Try
            'Send the email asynchronously
            smtpClient.SendAsync(mailMessage, userState)
        Catch smtpEx As SmtpException
            'Error handling here
        Catch ex As Exception
            'Error handling here
        End Try

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Any ideas?