What are the IP addresses of the WCO servers from which emails are sent? Specifically those associated with form submissions. Need to whitelist external IPs so that incoming mail 'originating' from the client's domain can make it through the spam blockers.
The best solution for preventing WCO emails from being blocked by spam blockers is to register a valid email sender address within WCO. You can refer to this article regarding the proper method to do this: