Google app script function to send emails from a spreadsheet.

sendEmailsFromSpreadsheet.js

/*
Structure of the spreadsheet

Email	                    Name	        Sending Status	 Email Send Date	               Source	   Lead Created Date	 Current Status
[email protected]	  Sony Mathew	  EMAIL_SENT	     Thu, 21 May 2020 08:20:37 GMT			                           EMAIL_SENT
*/


// All Contants here
var SPREADSHEET_URL = 'https://docs.google.com/spreadsheets/d/some-random-long-id/edit#gid=0';
var EMAIL_SENT = 'EMAIL_SENT';
var DO_NOT_SEND = 'DO_NOT_SEND';
var MAIL_SUBJECT = "{{firstName}}, Hi from Company";
var MAIL_TEMPLATE = "<b>Hello</b> {{firstName}}";

/**
 * Sends non-duplicate emails with data from the current spreadsheet.
 */
function sendEmailsFromSpreadSheet() {
  var spreadSheet = SpreadsheetApp.openByUrl(SPREADSHEET_URL);
  Logger.log(spreadSheet.getName());

  var sheet = spreadSheet.getActiveSheet();

  var startRow = 2; // First row of data to process
  var numRows = 5000; // Number of rows to process
  // Fetch the range
  var dataRange = sheet.getRange(startRow, 1, numRows, 7);
  // 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 fullName = row[1]; // Second column
    var sendStatus = row[2]; // Third column
    
    // Prevents sending duplicates    
    if (sendStatus !== EMAIL_SENT && sendStatus !== DO_NOT_SEND && !!emailAddress) {
      var person = personObject(emailAddress, fullName);
      var mail = mailObject(person);
      
      MailApp.sendEmail({
        to: person.email,
        subject: mail.subject,
        htmlBody: mail.content
      });
      sheet.getRange(startRow + i, 3).setValue(EMAIL_SENT);
      sheet.getRange(startRow + i, 7).setValue(EMAIL_SENT);
      sheet.getRange(startRow + i, 4).setValue((new Date).toGMTString());
      // Make sure the cell is updated right away in case the script is interrupted
      SpreadsheetApp.flush();
    }
  }
}

function personObject(email, fullName) {
  return {
    email: email,
    firstName: fullName.split(' ').slice(0, -1).join(' '),
    lastName: fullName.split(' ').slice(-1).join(' ')
  };
}

function mailObject(person) {
  return {
    subject: MAIL_SUBJECT.replace("{{firstName}}", person.firstName).replace("{{lastName}}", person.lastName),
    content: MAIL_TEMPLATE.replace("{{firstName}}", person.firstName).replace("{{lastName}}", person.lastName),
  };
}