BCC doesn't seem to function as an option of sendEmail - name and replyTo work though

function myFunction() {
  var ss = SpreadsheetApp.getActive();
  var sheet = ss.getSheetByName("Welcome");
  var targetSheet = ss.getSheetByName("Done");
  var startRow = 2;
  var lr = sheet.getLastRow();
  var dataRange = sheet.getRange(startRow, 1, lr-1, 6);
  var data = dataRange.getValues();
  var colNumber = sheet.getLastColumn()-1;
  var delRows = [];
  for (var i = 0; i < data.length; i++) {
  var row = data[i];
  var id = row[0];
  var emailAddress = row[1];
  var date = row[2];
  var city = row[3];
  var bccmail = row[6];
  var Sender = 'XXXXXX';
  var reply = 'xxxxxx@xxxxxxx.com';
  if (emailAddress.match('@')  === null){
  continue;
  };
  var subject = row[4];
  var message = "Hey " + id + ", welcome in the team " + row[5];
  MailApp.sendEmail(emailAddress, subject, message, {bcc: bccmail,name: Sender,replyTo: reply});
  var targetRange = targetSheet.getRange(targetSheet.getLastRow()+1, 1, 1, colNumber);
  var sourceRange = sheet.getRange(i+startRow, 1, 1, colNumber);
  sourceRange.copyTo(targetRange);
  delRows.push(i+startRow);
  } 
  delRows.reverse().forEach(ri=>{sheet.deleteRow(ri)});

Almost all the script works fine. When it comes to sendEmail, I have tried to follow these guidelines and use sendEmail(recipient, subject, body, options). 2 out of 3 options work fine but BCC doesn't work at the moment. Do you know what I am doing wrong? Can BCC be a variable?

The problem is in this line:

var bccmail = row[6];

dataRange is defined as a range with only 6 columns. data is a 2D array with the values of dataRange. row is a 1D array with a single row of data. JavaScript array indexes only start at 0, so the values are in row[0] to row[5].

Please check your sheet in which column does the bcc string is defined and count the index from 0.

Reference:

Arrays in JavaScript