[Area 1] Add note to MS 365 onboarding

Author: Maddy-Cloudflare

src/content/docs/email-security/deployment/api/setup/office365-graph-api.mdx

@@ -34,6 +34,12 @@ The Enterprise Applications that Email Security registers are not tied to any ad
 
 ## Set up Microsoft Graph API
 
+:::note
+
+[Zero Trust Email Security](/cloudflare-one/email-security/) users must delete their domains from the Area 1 portal before using [Microsoft API deployment](/cloudflare-one/email-security/setup/post-delivery-deployment/api/) in Zero Trust Email Security. You must remove the domain from the Area 1 portal, and complete the onboarding process in the Zero Trust dashboard. Once your new domain has been onboarded, all the information will be automatically updated.
+
+:::
+
 1. Log in to the [Email Security dashboard](https://horizon.area1security.com/).
 
 2. Go to **Settings** (the gear icon).