This may be caused by missing SPF or DKIM records. cPanel provides a tool to create these records automatically.
Once logged into cPanel you can go to Email Deliverability. You would click the repair button on the same row as the domain. (Green Arrows)
Please allow the system a few moments to repair/add the records. The page will auto-refresh and show if the repair succeeded. Please note this will only work if cPanel handles the DNS records for your domain. If you use 3rd party DNS you will need to manually copy the SPF/DKIM records to your DNS provider.
If you need further assurance please let us know by opening a Support Ticket.