Вот код:

Imports System
Imports System.Web
Imports System.Web.UI
Imports System.Web.UI.WebControls
Imports System.Web.UI.HtmlControls
Imports System.Data
Imports System.Data.OleDb
Imports System.Data.SqlClient
Imports System.IO
Imports System.Web.Mail
Imports Microsoft.VisualBasic

Public Class mail
Inherits System.Web.UI.Page
Protected WithEvents txtname As TextBox
Protected WithEvents txtsender As TextBox
Protected WithEvents txtcomment As TextBox
Protected WithEvents cmdsend As Button

Private Sub Page_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
'Put user code to initialize the page here
End Sub

Private Sub cmdsend_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles cmdsend.Click
Dim Msg As New MailMessage()
Msg.Subject = "Subject"
Msg.Body = txtname.Text & Chr(10)
Msg.Body &= txtcomment.Text
Msg.From = txtsender.Text
Msg.To = "samir_suleymanov@yahoo.com"
SmtpMail.SmtpServer = "192.168.11.136"
SmtpMail.Send(Msg)
End Sub
End Class

Выдает ошибку:

The server rejected one or more recipient addresses. The server response was: 550 5.7.1 Unable to relay for samir_suleymanov@yahoo.com