It's not currently possible for clients to import their own client lists in Phorest.
Example 1: many clients now have a form on their website which collects emails to sign up to newsletters.
Example 2: clients also use Mailchimp/other marketing platforms to collect client information that doesn't sync with Phorest.
Grönn(21212), for example would like the ability to be able to upload these lists herself to Phorest.