"The email address you requested is reserved" error

Issue

• Trying to create a new user with an email address that doesn't exist in the portal, raises an error.
• The error shown is "The email address you requested is reserved".
• The user cannot be created.

Environment

• Liferay DXP 7.0, 7.1, 7.2

Resolution

• Check if the email address is present in properties listed below.
  

  mail.session.mail.pop3.user 
  admin.reserved.email.addresses
  

• Check if any of the above properties exist in portal-ext.properties or portal-setup-wizard.properties.
• Delete or comment the value prior to create the user with the desired email address.
• Restart Liferay to apply changes.