Protected Sub SendMailBtn_Click(ByVal sender As Object, ByVal e As System.EventArgs) Handles SendMailBtn.Click

    Dim dt As DataTable = DirectCast((RadioButtonList1.SelectedValue.Select(DataSourceSelectArguments.Empty)), DataView).Table
    For Each dr As DataRow In dt.Rows
        Dim emailsender As String = "noreply@mymailhost.com"
        Dim emailRecipient As String = dr("Email").ToString()
        Dim UserName As String = "Dear " + dr("UserName").ToString() + ",<br/><br/>"
        Dim mm As New MailMessage(emailsender, emailRecipient)
        mm.Subject = mailSubject.Text
        mm.Body = UserName + mailBody.Text
        mailBody.Text = Replace(mailBody.Text, vbCrLf, "<br />")
        mm.IsBodyHtml = True
        Dim smtp As New SmtpClient()
        smtp.Send(mm)
    Next
    Response.Redirect("/MailSuccess.aspx")

End Sub


<asp:RadioButtonList ID="RadioButtonList1" runat="server">
       <asp:ListItem Value="sqldatasource1">Option 1</asp:ListItem>
       <asp:ListItem Value="sqldatasource2">Option 2</asp:ListItem>
       <asp:ListItem Value="sqldatasource3">Option 3</asp:ListItem>
</asp:RadioButtonList>