Post to https://uat-payments.lexisnexis.com/oobML/demo using their demo data
Result: Page displays successfully, only in new tab - not in iframe on same page

<?xml version="1.0" encoding="utf-8" ?>  
<multiLineFormPostRequest> 
<lexisNexisCode>34031</lexisNexisCode>  
<paymentLineItems>  
        <productLines>  
        <productAmount>25.00</productAmount>  
        <lexisNexisProductCode>Drivers License Renewal</lexisNexisProductCode>  
        <refField>permitID</refField>  
        <refField1>Mickey</refField1>  
        <refField2>Mouse</refField2>  
        <refField3>123456</refField3>
        <refField4 />  
        <refField5 />  
  </productLines>  
        <productLines>  
        <productAmount>45.00</productAmount>  
        <lexisNexisProductCode>Drivers License Renewal</lexisNexisProductCode>  
        <refField>permitID</refField>  
        <refField1>Minnie</refField1>  
        <refField2>Mouse</refField2>  
        <refField3>123456</refField3>
        <refField4 />  
        <refField5 />  
  </productLines>   
        <productLines>  
        <productAmount>85.00</productAmount>  
        <lexisNexisProductCode>Drivers License Renewal</lexisNexisProductCode>  
        <refField>permitID</refField>  
        <refField1>Minnie</refField1>  
        <refField2>Mouse</refField2>  
        <refField3>123456</refField3> 
        <refField4 />  
        <refField5 />  
  </productLines>   
        <productLines>  
        <productAmount>65.00</productAmount>  
        <lexisNexisProductCode>Drivers License Renewal</lexisNexisProductCode>  
        <refField>permitID</refField>  
        <refField1>Minnie</refField1>  
        <refField2>Mouse</refField2>  
        <refField3>123456</refField3>
        <refField4 />  
        <refField5 />  
  </productLines> 
</paymentLineItems>  
</multiLineFormPostRequest>