Dim message As New MailMessage("senderID@domainName.com",_
    "receiverID@domainName.com","subject of the Message ",_
    "body fo the message ")
/* create and add the attachment(s) */
Attachment attachment = new Attachment("sample.doc",
                        MediaTypeNames.Application.Octet)
  message.Attachments.Add(attachment)

/* create SMTP Client and add credentials */
Dim emailClient As New new SmtpClient("Your SMTP Server")

  /* Email with Authentication */
Dim SMTPUserInfo As New new NetworkCredential("userID", "password", "domainName")
emailClient.UseDefaultCredentials = False
emailClient.Credentials = SMTPUserInfo

/*Send the message */
emailClient.Send(message)