Sending a Email using Poco Library C++ (Gmail) - c++

Question

I tried this code but I get SMTP Exception, What could I do?
I tried changing the login id and password making sure they are the correct so.
If anyone knows what I can try to make it work I would be very grateful.
// compile with: g++ -Wall -O3 Email.cc -lPocoNet -lPocoFoundation -o Email && ./Email
#include <cstdlib>
#include <iostream>
#include <Poco/Net/SMTPClientSession.h>
#include <Poco/Net/MailMessage.h>
#include <string>
using namespace Poco::Net;
int main(int argc, char **argv)
{
std::string Username = "email_id";
std::string Password = "password";
std::string Receiver = "receiver#gmail.com";
std::string Name = "Charles";
std::string Subject = "Hello!";
std::string Content = "TEXT OF THE EMAIL";
try
{
MailMessage msg;
msg.addRecipient(MailRecipient(MailRecipient::PRIMARY_RECIPIENT, Receiver, Name));
msg.setSender(Username);
msg.setSubject(Subject);
msg.setContent(Content);
SMTPClientSession smtp("smtp.gmail.com");
smtp.login(SMTPClientSession::AUTH_LOGIN, Username, Password);
smtp.sendMessage(msg);
smtp.close();
std::cerr << "Sent mail successfully!" << std::endl;
}
catch (std::exception &e)
{
std::cerr << "Failed to send mail: " << e.what() << std::endl;
return EXIT_FAILURE;
}
return EXIT_SUCCESS;
}