[Email security] Add high-level overview (#26481)

Author: Maddy-Cloudflare

src/content/docs/cloudflare-one/email-security/setup/post-delivery-deployment/bcc-journaling/journaling-setup/m365-journaling.mdx

@@ -7,7 +7,9 @@ sidebar:
 
 import { GlossaryTooltip, Render } from "~/components";
 
-When you receive an email, the email lands on your Microsoft 365 inbox, and then Email security receives a copy of that email. The following email flow shows how this works:
+Microsoft 365 journaling is a post-delivery setup method that ensures a copy of every incoming and outgoing email is forwarded to Cloudflare for analysis. When you create a journal rule in the Microsoft Purview compliance portal, Cloudflare can scan messages that have already landed in your inbox.
+
+The following diagram shows how this works:
 
 ![Email flow when setting up Microsoft 365 with Email security.](~/assets/images/email-security/deployment/api-setup/journaling/Email_Security_MS365_Journaling_Diagram.png)
 
@@ -82,4 +84,4 @@ Once saved, the rule is automatically active. However, it may take a few minutes
 
 ## Next steps
 
-<Render file="email-security/enable-logs" product="cloudflare-one" />
+<Render file="email-security/enable-logs" product="cloudflare-one" />