Dim mail As New MailMessage()
Dim SmtpServer As New SmtpClient("smtp.gmail.com")
mail.From = New MailAddress(txtid.Text)
mail.[To].Add("Email Id to send@rediffmail.com")
mail.Subject = txtsub.Text
mail.Body = txtmess.Text
mail.Attachments.Add(New Attachment(OpenFileDialog1.FileName))
SmtpServer.Port = 587
SmtpServer.Credentials = New System.Net.NetworkCredential(txtid.Text, txtpass.Text)
SmtpServer.EnableSsl = True
SmtpServer.Send(mail)
mail.From = New MailAddress(txtid.Text)
MsgBox("E-mail Has Been Send Successfully !")
Its very simple to send email in vb.net please check this code or use directly.
If you are send attachment then use the openfiledialogbox control.