Journaling mail from Exchange 2013

Hi,

We are using Exchange 2013 CU9.

We are planned Journaling External mail’s (Outgoing/Incoming) for whole organization.

For Journaling External mail’s and other services, we have planned to go for third party solution.

We have standard CAL only. How to Journal only External mail’s to Journal mailbox because Standard Journaling supports at Mailbox Database Level.

Any suggestion please.. 

Thanks & Regards, Kumar N