I get those too, and I usually just delete the emails unless something in particular catches my eye (if one of my photographs is getting pinned a lot). I'm not sure how to turn that off.
However, the thing that's REALLY ANNOYING THE &*%$ out of me lately is "Related Pins." I hate them. Because I tend to look at Pinterest on my iPhone app when I have a few spare moments, it's impossible to thumbs-down related pins, and my feed is flooded with pins of people I'm not following. It is really peeving me, and I've sent Pinterest a polite but angry message. There needs to be a way to opt out of related pins. It's really ruining Pinterest for me.
*rant over*