Send mail automatic actuall

 // This constant is written in column C for rows for which an email

// has been sent successfully.

var EMAIL_SENT = 'EMAIL_SENT';

/**

 * Sends non-duplicate emails with data from the current spreadsheet.

 */

function sendEmails2() {

  var sheet = SpreadsheetApp.getActiveSheet();

  var startRow = 2; // First row of data to process

  var numRows = 20; // Number of rows to process

  // Fetch the range of cells A2:B3

  var dataRange = sheet.getRange(startRow, 1, numRows, 3);

  // Fetch values for each row in the Range.

  var data = dataRange.getValues();

  for (var i = 0; i < data.length; ++i) {

    var row = data[i];

    var emailAddress = row[0]; // First column

    var message = row[1]; // Second column

    var emailSent = row[2]; // Third column

    if (emailSent !== EMAIL_SENT) { // Prevents sending duplicates

      var subject = 'Sending emails from a Spreadsheet';

      MailApp.sendEmail(emailAddress, subject, message);

      sheet.getRange(startRow + i, 3).setValue(EMAIL_SENT);

      // Make sure the cell is updated right away in case the script is interrupted

      SpreadsheetApp.flush();

    }

  }

}