Problem in sending mail when i host my application

Imports System.Net.Mail
Imports System.Net
Partial Class _Default
    Inherits System.Web.UI.Page

    Protected Sub SendMail()
        ' Gmail Address from where you send the mail
        Dim fromAddress = "user@domain.com"
        ' any address where the email will be sending
        Dim toAddress = ("recevier@domain.com")

        Const fromPassword As String = "Password"
        ' Passing the values and make a email formate to display
        Dim subject As String = ("Abccc")
        Dim body As String = "this is body of your email " + vbLf
        ' smtp settings
        Dim smtp = New System.Net.Mail.SmtpClient()
        If True Then
            smtp.Host = "smtp.domainname.net"
            smtp.Port = 25
            smtp.DeliveryMethod = System.Net.Mail.SmtpDeliveryMethod.Network
            smtp.Credentials = New NetworkCredential(fromAddress, fromPassword)
            smtp.Timeout = 20000
        End If
        ' Passing values to smtp object
        smtp.Send(fromAddress, toAddress, subject, body)
    End Sub


    Protected Sub btn_Click(ByVal sender As Object, ByVal e As System.EventArgs) Handles btn.Click
        Try
            SendMail()
        Catch generatedExceptionName As Exception
        End Try
    End Sub
   
End Class