I'm setting up a real estate site with custom post types

I’m setting up a real estate site with custom post types and taxonomies. Users can search based on these taxonomies and text from specific fields. What I’d like to do, but can’t figure out how, is allow a visitor to subscribe for email alerts. So if they search for a 2 bed, 2 bath, single family, between 100-150k, there’s a nice little box that says “Get notified when more like this become available”, the input their email, and if the agent adds a new listing with matching criteria, an email goes out automatically to any customer who subscribed.

Anyone know of a way to do this or if there’s a plugin that can make it happen?