title: What is the difference between a SPF include: and a:?
body: <p>I have read through the documentation but the difference is still not very clear to me.</p>
  
  <p>My understanding is:
  1) include: will allow the IPs listed for the specified domain, and also any additional domains listed in that domain's own SPF records</p>
  
  <p>2) a: simply allows IPs listed for the specified domain</p>
  
  <p>Is that correct?</p>