Automate Email through vbscript

Hello,

I have the below email script:

Set fso=CreateObject("Scripting.FileSystemObject")

strSMTP="smtpserver.com"
strSubject="hello"
strRecipient=someone@aol.com,someone@smtpserver.com"
strSender="someone@smtpserver.com"
strBody="Hello"
strAttach="C:\test\testfile.pdf"

If fso.FileExists(strAttach) then
Set iMsg = CreateObject("CDO.Message")
Set iConf = CreateObject("CDO.Configuration")
iConf.Load -1    ' CDO Source Defaults
Set Flds = iConf.Fields
With Flds
    .Item("http://schemas.microsoft.com/cdo/configuration/sendusing") = 2
    .Item("http://schemas.microsoft.com/cdo/configuration/smtpserver") = strSMTP
    .Item("http://schemas.microsoft.com/cdo/configuration/smtpserverport") = 25
    .Update
End With
With iMsg
    Set .Configuration = iConf
    .To = strRecipient
    .CC = ""
    .BCC = ""
    .From = "<" & strSender & ">"
    .Subject = strSubject
    .TextBody = strBody
    .AddAttachment strAttach
    .Send
End With
Set iMsg = Nothing
Set iConf = Nothing
Else
MsgBox "The specified attachment does not exist"
End if


When I send to an AOL or yahoo account I receive the following error:
"The server rejected one or more recipient address.  The server response was: 553 sorry, that domain isn't in my list of allowed rcpthosts(#5.7.1)"

If I send this from my outlook using the same sender and smtp server it sends fine.  

Any help would be appreciated.

Thank you.