filter check_rdns phase connect match !rdns disconnect "550 no rDNS"listen on 0.0.0.0 inet4 port smtp tls pki pkiname filter { check_dyndns, check_rdns, check_fcrdns, senderscore, rspamd }Sometimes, it works fine. But sometimes, I get:May 27 02:36:55 mailserver smtpd[9850]: b972fe95620c78af smtp connected address=205.220.175.42 host=<unknown>
Sounds like DNS problem. Are you sure your dns server doesn't do some filtering of its own? Try to (temporarily) use different ones.
