SPF is used to verify if the IP address that is trying to send mails on behalf of a domain, which is allowed by that domain.
For Email Security users who use Office 365, incoming mail routes from Email Security to Office 365, and the sending IP of the original email will change to the Email Security IP. This results in SPF check failures for incoming emails from Trend Micro Email Security.
It is recommended to enable Enhanced Filtering for Connectors in Office 365. This feature will ensure the original sender's IP is preserved, preventing SPF check failures.
For detailed implementation steps, refer to Microsoft's guide on Enhanced Filtering for Connectors: