send_mail_jet_with_custom_header.rb

headers = {}
headers['X-MJ-CustomID'] = 'rubyPR_Test_ID_1469790724'
email = { from_email: "[email protected]",
          from_name: "Mailjet TEST",
          subject: 'Your email flight plan 23!',
          text_part: 'Dear passenger 1, welcome to Mailjet! May the delivery force be with you!',
          html_part: '<h3>Dear passenger 1, welcome to Mailjet!</h3><br />May the delivery force be with you!',
          recipients: [{:email => '[email protected]'}],
          CustomID: '1234567890',
          headers: headers
      }

variable = Mailjet::Send.create(email)