SQL & PL/SQL :: ORA-24247 With Valid ACL When Sending Smtp Mail?

I have users with the same privileges to the same ACL and some can send emails and some others cannot !

In principle I created the ACL for USER1:

BEGIN
dbms_network_acl_admin.create_acl
(acl=> 'mails_senden.xml',
description=> 'Mails senden ueber INTRANET Mail-Server ...',
principal=> 'USER1',
is_grant=> true,
privilege=> 'connect');
COMMIT;

[code]....

Then I added USER2:

BEGIN
dbms_network_acl_admin.add_privilege
(acl=> 'mails_senden.xml',
principal=> 'USER2',
is_grant=> true,
privilege=> 'connect');

[code]....

USER1 sent a mail via UTL_SMTP successful whereas USER2 got the errors:

DECLARE
*
ERROR at line 1:
ORA-24247: network access denied by access control list (ACL)
ORA-06512: at "SYS.UTL_TCP", line 17
ORA-06512: at "SYS.UTL_TCP", line 267

[code]....

There is still the following fact:

USER1 has the role DBA, USER2 got the EXECUTE privilege to packages UTL_TCP, UTL_SMTP (GRANT from SYS).

IF the role DBA was granted to USER2 too then he couldt send emails just as well as USER1.