Adding details about chat retention

Author: tomkau

articles/communication-services/concepts/join-teams-meeting.md

@@ -39,6 +39,12 @@ During a meeting, Communication Services users will be able to use core audio, v
 
 Additional information on required dataflows for joining Teams meetings is available at the [client and server architecture page](client-and-server-architecture.md). The [Group Calling Hero Sample](../samples/calling-hero-sample.md) provides example code for joining a Teams meeting from a web application.
 
+## Chat storage
+
+During a Teams meeting, all chat messages sent by Teams users or Communication Services users are stored in the geographic region associated with the Microsoft 365 organization hosting the meeting. For more information, review the article [Location of data in Microsoft Teams](/microsoftteams/location-of-data-in-teams). For each Communication Services user in the meetings, there is also a copy of the most recently sent message that is stored in the geographic region associated with the Communication Services resource used to develop the Communication Services application. For more information, review the article [Region availability and data residency](/azure/communication-services/concepts/privacy).
+
+If the hosting Microsoft 365 organization has defined a retention policy that deletes chat messages for any of the Teams users in the meeting, then all copies of the most recently sent message that have been stored for Communication Services users will also be deleted in accordance with the policy.  If there is not a retention policy defined, then the copies of the most recently sent message for all Communication Services users will be deleted after 30 days. For more information about Teams retention policies, review the article [Learn about retention for Microsoft Teams](/microsoft-365/compliance/retention-policies-teams).
+
 ## Diagnostics and call analytics
 After a Teams meeting ends, diagnostic information about the meeting is available using the [Communication Services logging and diagnostics](./logging-and-diagnostics.md) and using the [Teams Call Analytics](/MicrosoftTeams/use-call-analytics-to-troubleshoot-poor-call-quality) in the Teams admin center. Communication Services users will appear as "Anonymous" in Call Analytics screens. Communication Services users aren't included in the [Teams real-time Analytics](/microsoftteams/use-real-time-telemetry-to-troubleshoot-poor-meeting-quality).