Start by creating a new windows forms application and call it E-mail sender.

Now create your form as in the following picture:

Now go to the coding section. You do this by double clicking at the button.

This is the complete code:

Imports System.Net.Mail

Public Class Form1

    Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click

        Dim mymailmessage As New MailMessage()

        For i = 1 To Integer.Parse(TextBoxwiththenumbers.Text)

            Try

                mymailmessage.From = New MailAddress("youremail@gmail.com")  'has to be a gmail account

                mymailmessage.To.Add(TextBoxTo.Text)

                mymailmessage.Subject = TextBoxSubject.Text

                mymailmessage.Body = TextBoxBody.Text

                Dim Smtp As New SmtpClient("smtp.gmail.com")

                Smtp.Port = 587

                Smtp.EnableSsl = True

                Smtp.Credentials = New System.Net.NetworkCredential("youremail@gmail.com", "yourpassword") '   "Your gmail adress" , "Your password" 

                Smtp.Send(mymailmessage)

            Catch ex As Exception

            End Try

        Next

        MsgBox("Emails spammed !", MsgBoxStyle.Information, "lol")

    End Sub

    Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load

        MsgBox("Please wait while sending the mails, the program will not respond  while sending, so don't quit the program, just wait for a message saying the mail has been sent", MsgBoxStyle.Exclamation, "Warning")

    End Sub

    Private Sub Form1_FormClosing(ByVal sender As System.Object, ByVal e As System.Windows.Forms.FormClosingEventArgs) Handles MyBase.FormClosing

        Application.Exit()

    End Sub

End Class