title: Mailgun: Messages "Accepted" but taking long time to be delivered (or not being delivered)
body: <p>I'm using Mailgun for a site I maintain, usually Mailgun works great, but I am encountering a strange problem. My script calls the HTTP API to send messages using Mailgun, these then show up in my log as being "accepted", but then take a very long time to be "delivered", often failing to be delivered at all and simply remaining as "accepted". Has anyone experienced a similar error or could anyone suggest a way to fix it? I'm guessing it's in the arguments supplied to the API but I can't for the life of me figure out the problem.</p>
  
  <p>The problem exists for different recipient domains and different times of day.</p>
  
  <p>The JSON log of a problematic message is below. I have, of course, changed addresses and domains.</p>
  
  <pre><code>{
      "tags": [], 
      "timestamp": 1411498829.247304, 
      "envelope": {
          "targets": "my-own-email@address.com", 
          "transport": "", 
          "sender": "noreply@the-site-in-question.com"
      }, 
      "recipient-domain": "address.com", 
      "event": "accepted", 
      "campaigns": [], 
      "user-variables": {}, 
      "flags": {
          "is-authenticated": true, 
          "is-system-test": false, 
          "is-test-mode": false
      }, 
      "message": {
          "headers": {
              "to": "my-own-email@address.com", 
              "message-id": "20140923190027.112157.29352@the-site-in-question.com", 
              "from": "\"the-site-in-question.com\" &lt;noreply@the-site-in-question.com&gt;", 
              "subject": "Dom, your password was reset."
          }, 
          "attachments": [], 
          "recipients": [
              "my-own-email@address.com"
          ], 
          "size": 556
      }, 
      "recipient": "my-own-email@address.com", 
      "method": "http"
  }
  </code></pre>