Email campaigns are probably one of the most ignored things in your inbox, but a lot of effort goes into each message you send to spam. As far as digital careers go, this is one of the elders (about 40 years old!).
As a director of email marketing, it is your job to make engaging content that hopefully someone will actually look at. These directors have to predict and understand their target audience, create email campaigns, and make sure these campaigns get sent out at just the right time.
I believe this is a career that will be solid for quite some time. As long as people use their emails, companies will find a way to use that to sell things.