A ruby gem to look up the DMARC policy of any email service provider

To look up the DMARC policy of an email service provider, say yahoo.com, use

dmarc_inspector = DMARCInspector.new('yahoo.com')
dmarc_inspector.receiver_policy
# => :reject

If an email service provider doesn't have a DMARC policy, the DMARCInspector#receiver_policy method returns :none

See this spec for more examples

Add dmarc_inspector to your app's Gemfile

gem 'dmarc_inspector'

and run

bundle install

Wikipedia's article on DMARC and Postmark's post on DMARC are great articles to quickly understand DMARC.

To understand DMARC in entirety, I highly recommend reading RFC 7489. Its relatively short compared to most RFCs.