Script Task Email Send

Hello Creatio Community,

I'm creating a script task for email sender using a documentation from creatio team. I followed the provided instructions for creating the script task, but when I published  the script task some errors occured.

Some of the classes and interface cannot be found also the IntegrationApi library cannot be found.

source code below :

using System;
using System.Collections.Generic;
using System.Collections.ObjectModel;
using System.Drawing;
using System.Globalization;
using System.Linq;
using System.Text;
using Terrasoft.Common;
using Terrasoft.Core;
using Terrasoft.Core.Configuration;
using Terrasoft.Core.DB;
using Terrasoft.Core.Entities;
using Terrasoft.Core.Factories;
using Terrasoft.Core.Process;
using Terrasoft.Core.Process.Configuration;
using Terrasoft.Mail;
using Terrasoft.Mail.Sender;
using IntegrationApi;

    var mailBoxSettingId = Get("SenderMailbox");
    var emailClientFactory = ClassFactory.Get(
    new ConstructorArgument("userConnection", UserConnection));
    
    var emailSender = ClassFactory.Get(
    new ConstructorArgument("emailClientFactory", emailClientFactory),
    new ConstructorArgument("userConnection", UserConnection));
    var entity = UserConnection.EntitySchemaManager.GetInstanceByName("MailboxSyncSettings").CreateEntity(Uif (entity.FetchFromDB("Id", mailBoxSettingId, new List { "SenderEmailAddress" })) {
    var senderEmailAddress = entity.GetTypedColumnValue("SenderEmailAddress");
    var message = new Terrasoft.Mail.Sender.EmailMessage {
    From = senderEmailAddress,
    To = Get("Recipient").Split(';').ToList(),
    // Cc = List{ "first@recepient.co", "second@recepient.co"},
    // Bcc = List{ "first@recepient.co", "second@recepient.co"},
    Subject = Get("Subject"),
    Body = Get("Body"),
    Priority = Terrasoft.Mail.Sender.EmailPriority.Normal
    };
    var attachment = new Terrasoft.Mail.Sender.EmailAttachment {
    Id = Guid.NewGuid(),
    Name = "test.txt",
    Data = Encoding.ASCII.GetBytes("some test text")
    };
    message.Attachments.Add(attachment);
    emailSender.Send(message);
    }
    
    
    return true;


errors in lines :

    var emailClientFactory = ClassFactory.Get(
            var emailSender = ClassFactory.Get(
            var message = new Terrasoft.Mail.Sender.EmailMessage {
            Priority = Terrasoft.Mail.Sender.EmailPriority.Normal
            var attachment = new Terrasoft.Mail.Sender.EmailAttachment {

Documents in this link:
page 14: https://academy.creatio.com/docs/sites/academy_en/files/pdf/node/1474/Sending_emails_.pdf

https://academy.creatio.com/docs/7-18/developer/application_components/…