In my blog article „ Get a bullet proof email set up for spf-dkim-dmarc“, I explained how to setup your email account in order to be protected against spammer. I was following mainly the advices of postmark, which did an excellent job in this area.
In the meantime they published an introduction blog to DMARC which explains in all detail, how the mechanism is working. It’s well written and illustrated and you should take the time to read it, to understand the global approach against spammer.
The article can be found here.