When your ISPConfig mailserver sits behind a relayhost you'll get SPF failures as the relayhost is of course not part of the senders SPF records in their DNS. Rspamd can be configured to ignore given hostnames and check SPF against the host before the relayhost. Create file /etc/rspamd/local.d/external_relay.conf Code: # enable the module enabled = true; # rules are defined inside rules {} block rules { # this is the name of the symbol we will register EXTERNAL_RELAY_AUTHENTICATED { # a recognised strategy MUST be defined strategy = "hostname_map"; # there may be additional non/optional settings available particular to the strategy hostname_map = "/etc/rspamd/external_relay_hostname.map"; } } and create file /etc/rspamd/external_relay_hostname.map with a list of hostnames to ignore: Code: relayhostA.domain.tld relayhostB.domain.tld Restart the Rspamd service and you're done. More information can be found here: https://rspamd.com/doc/modules/external_relay.html
