Única função

function getMailBase() {
  var myspreadsheet = SpreadsheetApp.openById('CODIGO_DA_PLANILHA');
  var mysheet = myspreadsheet.getSheetByName("getMailBase");

  var start = 0;
  var max = 250;
  var count = 0;
  while (count < 999) {
    // var threads = GmailApp.getInboxThreads(start, max);
    var threads = GmailApp.search('category:promotions', start, max);
    if (threads.length == 0) break;
    var messages = GmailApp.getMessagesForThreads(threads);

    var messagesDataArray = [];
    for (var i = 0; i < threads.length; i++) {
      messagesDataArray.push([
        count,
        new Date(),
        messages[i][0].getDate(),
        messages[i][0].getSubject(),
        messages[i][0].getFrom(),
        messages[i][0].getReplyTo()
      ]);
    }

    mysheet.getRange(mysheet.getLastRow() + 1, 1, threads.length, messagesDataArray[0].length).setValues(messagesDataArray);
    Logger.log(new Date())
    start += max;
    count++;
  }
  mysheet.appendRow(["____________________", "____________________", "____________________"])
}