When using spamassisin in front of DirectAdmin, you see messages like:
2022-04-20 05:41:24 H=out7.antispamcloud.com [94.75.244.176] X=TLS1.2:ECDHE-ECDSA-AES128-GCM-SHA256:128 CV=no F=<info@email.ibood.com> rejected RCPT <recipient@example.com>: SPF: 123.123.123.123 is not allowed to send mail from email.ibood.com: Please see http://www.open-spf.org/Why : Reason: mechanism
2022-04-20 06:38:26 H=out7.antispamcloud.com [94.75.244.176] X=TLS1.2:ECDHE-ECDSA-AES128-GCM-SHA256:128 CV=no F=<fd_ochtendnieuws@messagent.fdmediagroep.nl> rejected RCPT <recipient@example.com>: SPF: 123.123.123.123 is not allowed to send mail from messagent.fdmediagroep.nl: Please see http://www.open-spf.org/Why : Reason: mechanism
This is because you need to add spamexperts to the safe senders (relayhost), this can be done as following:
edit this file: /etc/virtual/esf_skip_hosts
delivery.antispamcloud.com
*.antispamcloud.com
(Afterwards restart spamassassin)