It's possible for users to be sent an email notification whenever an asset they have previously downloaded has been changed.
You can choose to enable these based on when the original file for an asset is changed, when a new version of the asset is created, or both.
To configure these alerts simply visit Admin > System > New Content Notification Setting and select time limit values for the Notify downloader of file change time limit or Notify download of version change time limit settings.
0 is the default time limit value which disables the notifications completely.
In the above example, if a user has downloaded an asset within the last 30 days and the original file for that asset has changed, they will be sent a notification.
However, if they have downloaded any assets which have had new versions created they would not be notified.
Please note that the ability for users to receive email notifications from Asset Bank is still dependant on their individual account settings, specifically the 'System'