I've been using the free trial of Square Marketing, and it seems like a useful service with a fair price. The customization options are not very robust, but I'm getting good response with my first marketing email.

Unfortunately it does not offer a realistic ability to target only a subset of customers. Yes, there is an option to only send to those in a certain customer group. But without a way to automatically add customers to a group this is a terribly inefficient way of doing it.

Consider a beauty salon, for instance. Although primarily a service business, many also sell products. However there is a significant fraction of salon customers who will never purchase products. Including these customers in every marketing email related to products is likely to cause them irritation and to unsubscribe. They are then lost as a potential target for emails related to services, or general notices. But if the salon could create a customer group for "Product Buyers" and have customers automatically added to it when they purchase a product at the salon, then they could use Marketing much more effectively.

So my request: Please create a way for us to add customers to groups based on criteria we designate, rather than having to add them by hand individually. The most important designation, I feel, is whether they have purchased a particular item or an item from a particular category. And ideally, future customers would also be automatically added to such a group when their purchases meet that criteria.