Set up an IFTTT Gmail recipe that appends messages to Google Spreadsheet. Next, paste this script into that spreadsheet's Script Editor, and set a new trigger to fire when the document is changed.

google-apps-script.js

/*
  Spreadsheet Rows:
  -----------------------------
  A: timestamp (not used here)
  B: from
  C: subject
  D: label
  E: attachment name
  F: attachment url
*/

var API_KEY = "your_api_key",
    PROJECT_ID = "your_project_id",
    TIMEZONE_OFFSET = "-07:00", // US/Pacific PDT
    EVENT_COLLECTION = "messages";

function sendEvent(event) {
  var spreadsheet = SpreadsheetApp.getActiveSpreadsheet(), 
      sheet, last_row, values, timestamp, payload;

  // There are several change types to ignore
  if (event && (event.changeType == "EDIT" || event.changeType == "OTHER")) {
    Logger.log("Change detected...");

    sheet = spreadsheet.getSheets()[0];
    last_row = sheet.getLastRow();
    values = sheet.getRange(last_row, 1, 1, 6).getValues();
    
    timestamp = parseDate(values[0][0]);
    payload = JSON.stringify({
      "from": values[0][1] || "",
      "subject" : values[0][2] || "",
      "label": values[0][3] || "",
      "attachment": values[0][4] || "",
      "keen": {
        "timestamp": timestamp
      }
    });

    Logger.log("Sending event");
    Logger.log(payload);

    UrlFetchApp.fetch("https://api.keen.io/3.0/projects/" + PROJECT_ID + "/events/" + EVENT_COLLECTION, {
      "method" : "post",
      //"muteHttpExceptions": true, -- uncomment to avoid email error reports
      "contentType": "application/json",
      "headers": {
        "Authorization": API_KEY
      },
      "payload" : payload
    });

    // Deleting the last row triggers an error
    if (last_row !== 1.0) {
      Logger.log("Deleting this row");
      sheet.deleteRow(last_row);
    } else {
      Logger.log("Clearing this row");
      sheet.getRange(last_row, 1, 1, 6).clear();
    }
    
  } else {
    Logger.log("No change worth saving");
  }
}

// Reconstruct an ISO-8601 date string from IFTTT's format
function parseDate(str){
  var time = str.split(" "), months, timestring, parsed_hour,
      year, month, day, hour, minute, output;
  
  months = {
    "Jan": "01", "January": "01",
    "Feb": "02", "February": "02",
    "Mar": "03", "March": "03",
    "Apr": "04", "April": "04",
    "May": "05", 
    "Jun": "06", "June": "06",
    "Jul": "07", "July": "07",
    "Aug": "08", "August": "08",
    "Sep": "09", "Sept": "09", "September": "09",
    "Oct": "10", "October": "10",
    "Nov": "11", "November": "11",
    "Dec": "12", "December": "12"
  };
  
  year = time[2];
  month = months[time[0]];
  day = time[1].replace(",","");
  
  timestring = time[4].split(":");
  parsed_hour = (+timestring[0]).toFixed(0);
  
  if (time[4].indexOf("PM") > -1 && parsed_hour < 12) {
    hour = +parsed_hour + 12;
  } else {
    hour = parsed_hour;
  }
  
  minute = timestring[1].substring(0, timestring[1].length - 2);
  
  output = year + "-" + month + "-" + day + "T" + hour + ":" + minute + ":00" + TIMEZONE_OFFSET;
  //Logger.log(output);
  return output;
}