Code.gs

// Enter sheet name where emails are stored
var EMAILS_SHEET_NAME = "emails";
var REPORT_SHEET_NAME = "report";

var SCRIPT_PROP = PropertiesService.getScriptProperties(); // new property service

// This function glues spreadsheet and Apps Script project
// Run this function before everything else.
function setup() {
  var doc = SpreadsheetApp.getActiveSpreadsheet();
  SCRIPT_PROP.setProperty("key", doc.getId());
}

function sendEmails() {
  var doc = SpreadsheetApp.openById(SCRIPT_PROP.getProperty("key")); //// Alternatively, you can hard code spreadsheet's id here
  var sheet = doc.getSheetByName(EMAILS_SHEET_NAME);
  var columns = sheet.getRange(1, 1, 1, sheet.getLastColumn()).getValues()[0];

  if(columns.indexOf("Email") == -1 ){
    throw new Error("Email column not found.");
  }

  if(columns.indexOf("Last message") == -1 ){
    throw new Error("'Last message' column not found.");
  }

  //Loading data
  var data = {};
  var _data = sheet.getRange(2,1, sheet.getLastRow()-1, sheet.getLastColumn()).getValues();
  for (i in columns) {
    data[columns[i]] = _data.map(element => element[i]);
  }

  for(var i = 0; i < data['Email'].length; i++) {
    var today = Utilities.formatDate(new Date(), "UTC", "yyyy-MM-dd");
    if (parseInt(Utilities.formatDate(data['Last message'][i], "UTC", "yyyyMMdd")) < parseInt(today.replace(/([-])+/g, ""))) {

      // sheet.getRange(i+2, columns.indexOf("Last message")+1).setValue(new Date());
      var report = generateReport(data['City'][i], today);
      MailApp.sendEmail({
        to: data['Email'][i],
        subject: "Sales in " + data['City'][i] + " - " + today,
        htmlBody: report.body,
        inlineImages: report.images
      });
      SpreadsheetApp.flush();
    }

  }

}

function generateReport(city='London', day='1990-01-20') {
  var doc = SpreadsheetApp.openById(SCRIPT_PROP.getProperty("key"));
  var sheet = doc.getSheetByName(REPORT_SHEET_NAME);

  var incomes = {
    'Berlin': Math.round(sheet.getRange('D2').getValue()),
    'London': Math.round(sheet.getRange('J2').getValue()),
    'Warsaw': Math.round(sheet.getRange('P2').getValue())
  }

  var charts = {
    'Berlin': sheet.getCharts()[0],
    'London': sheet.getCharts()[1],
    'Warsaw': sheet.getCharts()[2]
  }

  var total_revenue = incomes[city];
  var chart = charts[city];

  var emailImages = {
    "chart": chart.getAs("image/png")
  };

  var reportBody = "Sales in " + city + " - " + day + "<br />";

  reportBody += "The daily revenue was " + total_revenue;
  reportBody += "<p align='center'><img src='cid:chart'></p>";

  return {
    "body": reportBody,
    "images": emailImages
  }
}