What is a No Effect Policy?
No Effect or P=none is a policy that lets you monitor the results of your SPF and DKIM without any impact on your emails which allows you to identify and authorize your genuine email-sending points.
This policy is the entry-level policy. No special treatment is required by receivers but enables a domain to receive feedback reports. The no-effect policy won't affect the delivery of your email, but it will provide you with reports on where your outbound email appears to be coming from.