One of the most common error using Fine Grained Acess and UTL_SMTP is the ORA-2927SMTP permanent error
This aren’t databae errors, this error are a generic authentication issue with the configuration of the SMTP server and fortunately, Oracle has a solution about it.

Contact your SMTP administrator for additional assistance as this solution may require your e-mail administrator to make the necessary changes.

More information :

• ORA-29279 SMTP: 554 Using Utl_smtp To Send Email (Doc)
• Document 604763.1 – Check SMTP Server Availability for ORA-29278 or ORA-29279 errors using UTL_SMTP to Send Email
• ORA-2427 con el paquete SMTP