Of the current email authentication mechanisms, SPF, DKIM, and DMARC, DKIM seems to be the most confusing for people (this is why we offer a human-powered DKIM checker, contact us for a free DKIM check). What is a DKIM selector? What are the DKIM tags? How does one create a DKIM record? Is there a good DKIM record generator? Here is a plain English explanation of DKIM, and a breakdown of the anatomy of a DKIM record.