[Email Security] Retro Scan note (#22379)

Author: Maddy-Cloudflare

src/content/docs/cloudflare-one/email-security/retro-scan.mdx

@@ -7,6 +7,10 @@ sidebar:
 
 Retro Scan allows you to scan up to 14 days of old messages in your Microsoft 365 inboxes and check if your current email security solution missed any threats. 
 
+:::note
+Retro Scan is only available for Microsoft 365 accounts.
+:::
+
 To start a free scan:
 
 1. Log in to [Zero Trust](https://one.dash.cloudflare.com/).