As I look at my Christmas tree that I still have not yet put away, it immediately brings me back to the family, shopping, stress and email that just ensued over the past few weeks. The volume of email that marketers sent during the holidays definitely spiked. Year-over-year increases were steady and Black Friday itself showed a 55% volume increase. When volume increases like this it’s even more difficult to stand out from the clutter of the inbox. So what did marketers do this holiday season....