Mail: Disable wp-mail.php when mailserver_url is mail.example.com.

git-svn-id: https://develop.svn.wordpress.org/trunk@39772 602fd350-edb4-49c9-b593-d223f7449a82

src/wp-mail.php

@@ -14,6 +14,12 @@
 if ( ! apply_filters( 'enable_post_by_email_configuration', true ) )
 	wp_die( __( 'This action has been disabled by the administrator.' ), 403 );
 
+$mailserver_url = get_option( 'mailserver_url' );
+
+if ( 'mail.example.com' === $mailserver_url || empty( $mailserver_url ) ) {
+	wp_die( __( 'This action has been disabled by the administrator.' ), 403 );
+}
+
 /**
  * Fires to allow a plugin to do a complete takeover of Post by Email.
  *