ImportCSV.js

function importCSVFromGmail() {
  var threads = GmailApp.search("redacted");
  var message = threads[0].getMessages().pop();

  var attachment = message.getAttachments()[0];

  if (attachment != null) {
    var attachName = attachment.getName();

    // Is the attachment a CSV file
    if (attachName.substring(attachName.length-4) === ".csv") {
      var id = "redacted";
      var name = "Data Sheet";
      var sheet = SpreadsheetApp.openById(id);
      var tab = sheet.getSheetByName(name);
      

      // Clear the content of the sheet
      var csvData = Utilities.parseCsv(attachment.getDataAsString(), ",");
      tab.getRange(1, 1, csvData.length, csvData[0].length).setValues(csvData);
    }
  } 
}