What is SMTP server host name for webmail

<pre>Using mm As New MailMessage("info@ntrading.com", "aaa@gmail.com")
                filePath = Application.StartupPath + "\\PaySlip\\" + PaySlipName + ".pdf"
                mm.Subject = "test"
                mm.Body = "Checking"
                mm.Attachments.Add(New Attachment(filePath))
                'For Each filePath As String In openFileDialog1.FileNames
                '    If File.Exists(filePath) Then
                '        Dim fileName As String = Path.GetFileName(filePath)
                '        mm.Attachments.Add(New Attachment(filePath))
                '    End If
                'Next
                mm.IsBodyHtml = False
                Dim smtp As New SmtpClient()
                smtp.Host = "secure.webmail.com"
                smtp.EnableSsl = True
                Dim NetworkCred As New NetworkCredential("info@ntrading.com", "xxxxx123")
                smtp.UseDefaultCredentials = True
                smtp.Credentials = NetworkCred
                smtp.Port = 25

                smtp.Send(mm)
                MessageBox.Show("Email sent.", "Message")
            End Using