In the world of online business email is King.
Despite the fact that every social network offers advertising, email is still the winner. Email still boasts the highest eCommerce conversion rates
You can promote Pins, retarget on Facebook, and pay for Discovery on StumbleUpon. All these options are exciting advertising avenues that work. They all still pail in comparison to good old email.
There are many studies supporting emails superior conversion rates. In particular this graph, from Statista, it shows the conversion rates of US online shoppers.