This is happening because SmarterTools made some recent changes to SmarterMail 16x in the way that they validate trusted senders. If a trusted sender or trusted domain fails the SPF or DKIM check they are considered untrusted and will still be marked as spam if they are sending from unauthorized IP addresses or we're detecting a DKIM failure. The only way around this at this time is to whitelist the IP of the sender in SM so that all anti-spam checks are bypassed.