System Module Email - How to get the primary source of an Email Outbox record

[akqck]

Hello,

for a customer extension I need to know the primary source of an "Email Outbox" (t8888) record in the "Email Editor" page.
In table 8909 "Email Related Record" the information is available.
But the table Access = Internal.

How can I solve this?

I'm looking for a function like GetEmailRelatedRecords.

Thank you.