Providing an empty string is not allowed and will result in the default URL being used. Furthermore the page the URL links to should preferably be localized in the site language.


If a WordPress site had its URL changed from HTTP to HTTPS, by default this will return true. This filter can be used to disable that behavior, e.g. after having replaced URLs manually in the database.


Returning a non-null value will short-circuit wp_mail(), returning that value instead. A boolean return value should be used to indicate whether the email was successfully sent.


The dynamic portion of the hook name, $action, refers to the post action. Possible filter names include:

  • wp_handle_sideload_overrides
  • wp_handle_upload_overrides