Index: enrol/paypal/ipn.php
===================================================================
--- enrol/paypal/ipn.php	(revision 18727)
+++ enrol/paypal/ipn.php	(working copy)
@@ -170,7 +170,8 @@
 
         }
 
-        if ($data->business != $plugin->get_config('paypalbusiness')) {   // Check that the email is the one we want it to be
+        $textlib = textlib_get_instance();
+        if ($textlib->strtolower($data->business) != $textlib->strtolower($plugin->get_config('paypalbusiness'))) {   // Check that the email is the one we want it to be
             message_paypal_error_to_admin("Business email is {$data->business} (not ".
                     $plugin->get_config('paypalbusiness').")", $data);
             die;