How to distinguish who is a customer?
What is common practice for distinguishing who is a customer? For example, I have a client who wants to make sure that an event invitation they are sending goes to their customers - but although they have 3 fields called "customer" or "is customer" or similar, none appear to have been used with any consistency in the past and I'm wondering what to suggest implementing going forward. This must be a common need. Thanks for any input!