Some contact groups are built-in to the Echo Texting app and cannot be edited by the admin. The built-in groups include "All Contacts" and "Sandbox". The All Contacts group is exactly what it sounds like. You can use this group to send a text to all of your contacts at once. The Sandbox group is a special test group the admin may send texts to for testing purposes. If you wish to perform testing without wasting text credits use the sandbox group feature.