[Email Security] Impersonation registry nuances (#17519)

Author: Maddy-Cloudflare

src/content/docs/cloudflare-one/email-security/detection-settings/impersonation-registry.mdx

@@ -11,6 +11,7 @@ The impersonation registry contains combinations of emails of users who are like
 
 The impersonation registry should contain a list of users who are likely to be impersonated. Email Security applies enhanced security to variations of registered email addresses for additional [Business Email Compromise (BEC)](https://www.cloudflare.com/en-gb/learning/email-security/business-email-compromise-bec/) protection.
 
+For easier tracking, the Email Security team recommends syncing and structuring VIPs in groups, and avoid doing manual inputs of users.
 :::
 
 To add a user to the impersonation registry: