ORA-24247: network access denied by access control list (ACL) using a database procedure

@&lt

We have recently upgraded from database version 10.2.0.4 to 11.1.0.7. We use many packaged procedures that create files
on the server and the procedures send me an email with a file link to the files. After reading the 11g security features
i realised 11G now uses Fine-Grained Access to external network services using ACL. I read Document ID 557070.1 and setup the following ACL:

conn sys/<password>@&lt;db> as sysdba
set serveroutput on

show user;

create or replace procedure mailserver_acl(
  aacl       varchar2,
  acomment   varchar2,
  aprincipal varchar2,
  aisgrant   boolean,
  aprivilege varchar2,
  aserver    varchar2,
  aportlow   number,
  aporthigh  number)
is
begin 
  begin
    DBMS_NETWORK_ACL_ADMIN.DROP_ACL(aacl);