CDOSYS: No email is getting sent

Hi all.

I am trying CDOSYS code to send out email.
The problem is when I try to send email to gmail and hotmail account, it never works.
Means, no email appears at gmail and hotmail account.
But when I send it to yahoo mail, it works.
I run the code at localhost. I use Win XP Pro.
I just wonder why this happen.
Can someone explain to me ?

Below is the code that Im trying out :

Code:

---

<%
        '----------------------------------------------------------------------------
        '
        '        Send email using the CDOSYS component
        '
        '        by Chris Hardy
        '        http://www.chrishardy.co.uk/
        '
        '----------------------------------------------------------------------------

  Option Explicit

  dim sName, sEmail, sMessage
        dim oCdoMail, oCdoConf, sConfURL

  if Request.Form("Action") <> "" then
    sName = Request.Form("Name")
    sEmail = Request.Form("Email")
    sMessage = Request.Form("Message")

                Set oCdoMail = Server.CreateObject("CDO.Message")
                Set oCdoConf = Server.CreateObject("CDO.Configuration")

                sConfURL = "http://schemas.microsoft.com/cdo/configuration/"

                with oCdoConf
                        .Fields.Item(sConfURL & "sendusing") = 1
                        .Fields.Item(sConfURL & "smtpserver") = "localhost"
                        .Fields.Item(sConfURL & "smtpserverport") = 25
                        .Fields.Update
                end with

                with oCdoMail
                        .From = "[email protected]"
                        .To = sEmail
                        .Subject = "My message subject"
                        .TextBody = sMessage
                        .HTMLBody = sMessage
                        .Configuration = oCdoConf
                        .Send
                end with

                Set oCdoConf = Nothing
                Set oCdoMail = Nothing

    response.write "Thanks for your message!"
  else
%>
<form method="post" action="<%=Request.ServerVariables("SCRIPT_NAME")%>">
<p>Name:<br /><input type="text" name="Name" /></p>
<p>E-mail:<br /><input type="text" name="Email" /></p>
<p>Message:<br /><textarea name="Message"></textarea></p>
<p><input type="submit" name="Action" value="Send" /></p>
</form>
<%
  end if
%>

---