Script to send confirmation e-mail not working

I am using the following script which I got off the internet to send a confirmation e-mail to clients after they have filled in my form.  The problem is that though the script report no errors the e-mails are not received and may well not be sent.  Is there someway I can tell whether the e-mails are at least sent?  What could the problem possibly be?

Const cdoSendUsingPickup = 1
Const cdoSendUsingPort = 2
Const cdoSendUsingExchange = 3

Const cdoAnonymous = 0
Const cdoBasic = 1
Const cdoNTLM = 2

'Sends an email To aTo email address, with Subject And TextBody.
'The email is In text format.
'Lets you specify BCC adresses, Attachments, smtp server And Sender email address

  on error resume Next

  Dim Message 'As New CDO.Message '(New - For VBA)
 
  'Create CDO message object
  Set Message = CreateObject("CDO.Message")

  'Set configuration fields.
  With Message.Configuration.Fields
    'Original sender email address
    .Item("http://schemas.microsoft.com/cdo/configuration/sendemailaddress") = "myemail@yahoo.com"

    'SMTP settings - without authentication, using standard port 25 on host smtp
    .Item("http://schemas.microsoft.com/cdo/configuration/sendusing") = cdoSendUsingPort
    .Item("http://schemas.microsoft.com/cdo/configuration/smtpserverport") = 25
    .Item("http://schemas.microsoft.com/cdo/configuration/smtpserver") = "smtp.btl.net"

    'SMTP Authentication
    .Item("http://schemas.microsoft.com/cdo/configuration/smtpauthenticate") = cdoAnonymous

    .Update
  End With

  'Set other message fields.
  With Message
    'From, To, Subject And Body are required.
    .From = "myemail@yahoo.com"
    .To = "myemail@yahoo.com"
    .Subject = "Land Registry Application re Parcel " + request.form("PARCELNO") + "in Reg. Section " + request.form("REG_SECTION")

    'Set TextBody property If you want To send the email As plain text
    .TextBody = "This is to confirm receipt of your application(s)."

    'Set HTMLBody  property If you want To send the email As an HTML formatted
    '.HTMLBody = TextBody

    'Blind copy And attachments are optional.
    'If Len(BCC)>0 Then .BCC = BCC
    'If Len(Files)>0 Then .AddAttachment Files
   
    'Send the email
       response.write("before sending")
    .Send
    response.write("after sending")
  End With

  'Returns zero If succesfull. Error code otherwise
  SendMailByCDO = Err.Number