From the webserver logs:
77.43.51.66:40000] PHP Warning: Declaration of Mailforwardfrom::permalink($domain, $mailforward = false, $absolute = false) should be compatible with Domain::permalink($domain_name = NULL, $absolute = false) in /panel/include/class- Mailforwardfrom.php on line 67, referer: https://example.it/mailforward.php/succhia.cz/asd