title: How to use Mailgun with HTTParty in Rails
body: <p>I want to use Mailgun with HTTParty in Rails:</p>
  
  <pre><code>RestClient.post "https://api:key-###"\
      "@api.mailgun.net/v3/###/messages",
      from: from_email,
      to: to_email,
      subject: title,
      html: body_text
  </code></pre>
  
  <p>It's working but</p>
  
  <pre><code>payload = {
      from: email_history.from_email,
      to: email_history.to_email,
      subject: email_history.title,
      html: email_history.body_text,
      multipart: true
  }
  
  response = SendEmailJob.post('https://api:key-###'\
  '@api.mailgun.net/v3/###/messages', payload)
  </code></pre>
  
  <p>Returns:</p>
  
  <pre><code>{
    "message": "'from' parameter is missing"
  }
  </code></pre>
  
  <p>I checked and the payload "from" parameter exists.</p>
  
  <p>How can I fix this?</p>