title: How to maximize deliverability through Amazon SES? DKIM, SPF, Sender Id or all of them?
body: <p>I'm working on a digital gifting platform that relies on email reaching the inbox.  Email is sent through Amazon SES, and has high quality (recipient's name in the email, single recipient, personally crafted message, extremely low bounce and complaint rate).  However, I am still seeing very mixed results as to spam filter behaviour.  Some get marked as spam some don't on the same ISPs.</p>
  
  <p>I currently have no DKIM, SPF, or Sender ID set (<a href="http://docs.aws.amazon.com/ses/latest/DeveloperGuide/authentication.html" rel="nofollow">http://docs.aws.amazon.com/ses/latest/DeveloperGuide/authentication.html</a>)</p>
  
  <p>Is there any downside to using all of these together, or should I pick and choose?</p>