Use Brandkit's Email Users function.
Email Users can be used to email, All Users, All users that have previously downloaded the selected assets or to a specific User Role (e.g. Staff).
Email Users is initiated by an Admin user (it's not automatically triggered by uploading a new Version).
1. Select the Asset you want to update.
2. Edit the Asset > Select Upload New Version - this will update the Asset's original file, storing the previous version for rollback if required, but will maintain the existing Asset ID and Tags etc.
3. With the edited Asset (or multiple edited Assets selected) in the basket, click the Email Users button to display the Email Users modal window.
4. In the Recipients dropdown - select the "All users who have previously downloaded these assets" option.
5. Type a suitable message
6. Click Send Email.
This will send the email to any users who has downloaded one or more of the selected assets.
Note: if you don't use Versioning but instead create a new Asset (with the intent of archiving the old asset), then you would need to have both the new and old assets selected - in order for your email to reach users who previously downloaded the old asset.
While Email Users is initiated by an Admin, there is also automatic Recommended Notifications triggered when you either (a) change the Expiry date or (b) change the Licence of an asset. These are not triggered by uploading a new version.
Recommended Notification are addressed to any user that has previous downloaded that particular Asset. An Admin then has to Approve the Recommended Notification before it is sent to Users.