title: X-Message-Delivery in Hotmail Messages
body: <p>Recently I stared deciphering the hotmail inbox/junk folder placement. After long searching I found out that Hotmail/Outlook is using their X-Message-Delivery tag they input in each mail, to determine alot of things. If you go to source of an e-mail you can see an X-Message-Delivery similar to this : </p>
  
  <p><code>Vj0xLjE7dXM9MDtsPTE7YT0wO0Q9MjtHRD0yO1NDTD00</code> </p>
  
  <p>which if you BASE64-Decode it you get </p>
  
  <p><code>V=1.1;us=0;l=1;a=0;D=2;GD=2;SCL=4</code></p>
  
  <p>Based upon my research, I found out that following things are causing a message to go to the junk folder,</p>
  
  <pre><code>If "D=x" is higher then 1
  If "GD=x" is higher then 1
  If "SCL=x" is higher then 0
  </code></pre>
  
  <p>Other then that I found out that V=1.1 is allways the same and does not change in any e-mail I received (or atleast the ones I checked)</p>
  
  <p>I think that "a=x" is meaning if the sender is in the receivers adressbook, or is atleast known by the receiver. If its 0 its a new sender, and therefor more likely to go to the junk folder, if its a=1 it helps to get into inbox.</p>
  
  <p>I think the l=1 or l=0 has something to with, if images are blocked or not for this sender upon an open. Although I did not find this very consistent.</p>
  
  <p>Does any of you know, what these tags stand for?</p>
  
  <pre><code>D=
  GD=
  us= 
  </code></pre>
  
  <p>If you do, do you also know what they would change from 0 to 1 or 2 ?</p>
  
  <p>Thank u!</p>