add a parameter in the contact list request to search with the emails
Don't limit it to email but also 'name' property or any other identifier for a contact search mechanism.
While a proper Contact Search endpoint in the API is in our backlog, it is possible to search a contact by email using the email address as a resource alias.Sending the request GET https://api.frontapp.com/contacts/alt:email:email@example.com will try to fetch a contact with the email address firstname.lastname@example.org. If no contacts exist, the API will respond with a 404 error.
Note that you can use the same logic with other types of handles too.