Can you have multiple Oracle ACL files?

Question

I have an application which needs to send emails through Oracle triggers. I understand that in Oracle 11g you must have an ACL file to grant certain schemas access to the network. My plan was to create a separate ACL file for each user that needs access to the network, and then check that it has been created properly by using the following query:

SELECT * FROM DBA_NETWORK_ACLS;

However, it seems that only one record is ever returned for this query - always the latest ACL that's been created. Does this mean that you can only ever have one ACL? If so, presumably this means that when installing this application on a client's server, I must just add privileges to their existing ACL rather than trying to create a new one?

Thanks!

UPDATE

These are the commands I'm using:

--create ACL for USER1
DBMS_NETWORK_ACL_ADMIN.CREATE_ACL(ACL => 'testacl1.xml', 
                                  DESCRIPTION => 'ACL',
                                  PRINCIPAL   => 'USER1',
                                  IS_GRANT    => TRUE,
                                  PRIVILEGE   => 'connect');
DBMS_NETWORK_ACL_ADMIN.ADD_PRIVILEGE(ACL => 'testacl1.xml',
                                     PRINCIPAL => 'USER1',  
                                     IS_GRANT  => TRUE,  
                                     PRIVILEGE => 'resolve'); 
DBMS_NETWORK_ACL_ADMIN.ASSIGN_ACL(ACL => 'testacl1.xml', host => '*'); 

--create ACL for USER2
DBMS_NETWORK_ACL_ADMIN.CREATE_ACL(ACL => 'testacl2.xml', 
                                  DESCRIPTION => 'ACL',
                                  PRINCIPAL   => 'USER2',
                                  IS_GRANT    => TRUE,
                                  PRIVILEGE   => 'connect');
DBMS_NETWORK_ACL_ADMIN.ADD_PRIVILEGE(ACL => 'testacl2.xml',
                                     PRINCIPAL => 'USER2',  
                                     IS_GRANT  => TRUE,  
                                     PRIVILEGE => 'resolve'); 
DBMS_NETWORK_ACL_ADMIN.ASSIGN_ACL(ACL => 'testacl2.xml', host => '*');

The problem is that testacl2 seems to be overwriting testacl1. Does this mean that I can only have one ACL file, or one ACL file per host?