The CA feed feature is a generic product feature where we send changed Calculated Attribute data along with user identities (because they are needed to identify users) to the event forwarders.
For some forwarders like Braze, both user identities (externalID & email) are sent. This can lead to significant data volumes to be sent to Braze and the client to incur unneeded costs due to email being charged as a data point.
As the external_id is only needed for the user track endpoint, we can use Data Filters to exclude sending email (user identity) by filtering that off. Even if the option for "Include Enriched User Identities" is checked off in the Connection Settings, we would need the email user identity to be filtered OFF to prevent it being forwarded.