When an admin adds a teammate to their account, they're able to restrict the teammate's permissions to certain lists of contacts.
Teammates can only send messages to contacts on the lists they have access to. The same applies to inbound messages.
For this reason, we highly recommend granting teammates full list permissions. Otherwise, they may miss out on some messages.
You should only restrict list permissions if your teammate plans to send campaigns to large groups, and you don't want them to accidentally send a message to the wrong list.