Codenstuff.com

A from address must be specified

Imports System.Net.Mail
Public Class Form1

    Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
        Timer1.Enabled = False
    End Sub

    Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
        Timer1.Enabled = True
    End Sub
    Private Sub Timer1_Tick(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Timer1.Tick
        Dim smtp As New System.Net.Mail.SmtpClient("smtp.gmail.com", 587)
        Dim spam As Integer = amount.Text
        Dim smtpserver As New SmtpClient()
        Dim mail As New MailMessage()
        smtpserver.Credentials = New Net.NetworkCredential("MYEMAILADRESS@gmail.com", "MYPASSWORD")
        smtpserver.Port = 587
        smtpserver.Host = "smtp.gmail.com"
        smtpserver.EnableSsl = True
        If spam = 0 Then
            Timer1.Enabled = False
        Else
            mail.Subject = subject.Text
            mail.To.Add(whoto.Text)
            mail.Body = body.Text
            smtpserver.Send(mail)
            spam += -1

        End If

    End Sub

    Private Sub body_TextChanged(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles body.TextChanged

    End Sub
End Class

mail.From = New MailAddress("user@source", "user")