Sending mails from Google Sheets

sheetmail.gs

// This constant is written in column C for rows for which an email
// has been sent successfully.
var EMAIL_SENT = "EMAIL_SENT";
var RESULTCOL = 15; // O
var ASSIGNMENT = "09 - Blindwalk";
var SUBJECT = "[MATLAB] Assignment " + ASSIGNMENT;

var messages = {
  '1': "You successfully passed assignment " + ASSIGNMENT + ". Congrats!\n",
  '1?': "You passed assignment " + ASSIGNMENT + ". We want to note that it was a rather close call. If you want more specific feedback come up to us in class/after lecture or send an email.\n",
  '0': "You failed assignment " + ASSIGNMENT + ". Sorry about that. If you are interested in more specific feedback and want to talk about the stuff you struggled with come up to us in class/after lecture or send an email.\n"
};

function sendEmails() {
  var sheet = SpreadsheetApp.getActiveSheet();
  var startRow = 33;  // First row of data to process
  var numRows = 30;   // Number of rows to process
  
  var dataRange = sheet.getRange(startRow, 1, numRows, RESULTCOL+1);
  var data = dataRange.getValues();
  
  // List of registered aliases in Gmail. 'from' needs to match one of those.
  //var aliases = GmailApp.getAliases()
  //Logger.log(aliases);

  for (var i = 0; i < data.length; ++i) {
    var row = data[i];
    Logger.log(row)
    var emailAddress = row[3] + '@uos.de'; // C
    var emailSent = (row[RESULTCOL] == EMAIL_SENT); // F
    var state = (row[RESULTCOL-1] === 1 ? 'pass' : (row[RESULTCOL-1] === '1?' ? 'close' : (row[RESULTCOL-1] === 0 ? 'fail' : 'noncompete')));
    if ('noncompete' !== state && !emailSent) {
      var message = "Hey " + row[1] + "!\n"; // A, Firstname
      message += messages[row[RESULTCOL-1]];      
      message += "\nThis is an automated message. If something doesn't feel right about it, contact us.\nGood luck with the current and all coming assignments!\n Andrea and Alex";
 
      GmailApp.sendEmail(emailAddress, SUBJECT, message, {
        from: "",
        replyTo: "",
      });

      sheet.getRange(startRow + i, RESULTCOL+1).setValue(EMAIL_SENT); // Col right of the results
      SpreadsheetApp.flush();
    }
  }
}