Email notifications are not sent on instances running with ORACLE

Precondition: Have a fresh instance of XWiki 9.11RC1 configured with ORACLE (11.2) Database.

1. Login as Admin
2. Configure the mail sending settings (Administer Wiki > Mail > Mail Sending)
   Email server: smtp.gmail.com
   Email server port: 587
   Email server username: yourusername@gmail.com or @xwiki.com
   Email server password: yourpassword
   Additional Properties: mail.smtp.starttls.enable=true
3. Create an user (e.g. U1) with a valid email address
4. Login with the user
5. Click on the Watchlist bell
6. Click on Settings, in the right side of Notifications
7. Set 'Email Frequency' to 'Hourly' and 'Details of the changes' to 'Standard'
8. Set all Pages Notifications to ON (menu and e-mail)
9. Click on the Watchlist bell and turn 'Watch this wiki' toggle to ON
10. Login with Admin
11. Create, update, comment and delete a page
12. Trigger "Notifications hourly email" from Job Scheduler (/xwiki/bin/view/Scheduler/)
13. Check the email notifications for the user U1

EXPECTED RESULTS

On the address set on his profile, the user receives a notification email containing the events performed by Admin (create, update, comment and delete a page).

ACTUAL RESULTS

No notification mail is received.

I've tested also on MySQL, PostgreSQL and HSQL, but it seems that the issue is reproducing only on Oracle. No errors in the logs.