the email property should be a list of emails

Other fields like phone-numbers and enckeys already are lists. Making the email field an "emails" list field would be a good idea as there might be more than one email per organisation (and therefore a reason for multiple enckeys). You could store multiple emails comma separated but then a client has to parse this list if he wants to know which encryption key is used for a specific email address, etc.

Start by locating the data definition and client-facing entry points for the email, phone-numbers, and enckeys fields. Review how existing list fields are represented, then define what it means for multiple emails to map to their encryption keys; done means the schema and consuming clients consistently support that relationship.

Written by the indexing model from the issue text.