I try send mail from APEX (apex_mail.send) and I have in Manage Instance -> Manage Meta Data -> Mail Queue list of mails with error: ORA-28239: no key provided
Oracle Docs give the following recommendation:
ORA-28239: no key provided
Cause: A NULL value was passed in as an encryption or decryption key.
Action: Provide a non-NULL value for the key.
Where do I 'Provide' the non-NULL value and where is this derived?