Senta has an option to restrict practice users, so that they can only work with certain clients - it's ideal for subcontractors or external agency staff.
This feature will allow you to set practice users as "restricted" users. This means that he or she can only see certain clients -- the ones where they have a role on that client, e.g. account manager or a specialist role.
For example, suppose you had a subcontractor, Bob, who only did work for two clients, Acme Ltd and Zenith Ltd. You would set Bob as a restricted user, and then he would not be able to see any clients. Then, you could add Bob as account manager for Acme & Zenith, and he would see only those two clients.
Restricted users are also only able to view tasks assigned to them if they are the account manager or specialist for a client. The practice outbox is not available to restricted users.
If you decided to give Bob work for another client, Pinnacle Ltd, again, you just add Bob as account manager and he would now see Acme, Pinnacle and Zenith.
You can turn this feature on by going to Settings > General settings > Extras and turning on the restricted users option.
You can set users to be restricted by going to Settings > Users > Click on a user. From here select "restricted user" from the dropdown "role" menu.
Note - when you add / remove clients, the restricted user must sign out and sign in again to pick up the changes.