In this documentation, we can learn how to ban emails in phpBB.
1) Login to phpBB admin panel.
2) Go to the tab ‘Users and Groups’.
3) Select the option ‘Ban Emails’ from the section ‘User Security’.
4) Enter the email addresses and details.
5) Click the button ‘Submit’.
6) If you want to unban any banned mails, you can do it from the section ‘Unban or Unexclude emails’.
That is how we can ban email addresses in phpBB.
If you need any further assistance please contact our support department.