You could try authentification via "App password".

On your Google account:

1. set "2-Step Verification" ON 2-Step Verification

2. create 16-character "App password"( How to create app password) -> result should be similar to: 16-character "App password"

3. Instead of Google account password use 16-character password

   MailMessage mail = new MailMessage();
   foreach (string receiver in DolociPrejemnike())
       mail.To.Add(receiver);
   mail.From = new MailAddress("app_gmail@gmail.com", "No replay"); //pošiljatelj (vedno enak)
   mail.Subject = SetSubject();
   mail.Body = SetBody();
   mail.IsBodyHtml = true;
   
   SmtpClient smtp = new SmtpClient();
   smtp.Host = "smtp.gmail.com";
   smtp.Port = 587;
   smtp.UseDefaultCredentials = true;
   smtp.Credentials = new System.Net.NetworkCredential("app_gmail@gmail.com", "xtqapucsmyvqmvxp"); // Enter seders User name and password  
   smtp.EnableSsl = true;
   smtp.Send(mail);
   

So thanks for all the replays! i have fixed this issue by doing this:

I have enabled the "App password for windows machines" Then i simply changed the password from the email password to the google generated one

and changed the code to the following:

public class JavaMailUtil {
public static void sendMail(String recepient,String order) throws Exception {

    Properties properties=new Properties();
    properties.put("mail.smtp.auth", "true");
    properties.put("mail.smtp.starttls.enable", "true");
    properties.put("mail.smtp.host", "smtp.gmail.com");
    properties.put("mail.smtp.port", "587");
    String myAccountEmail="yourEmailAddress@gmail.com";
    String password="Generated Windows machine password from google";
    Session session=Session.getInstance(properties, new Authenticator() {
        @Override
        protected PasswordAuthentication getPasswordAuthentication() {
            return new PasswordAuthentication(myAccountEmail, password);
        }
    });
    
    Message message=prepareMessage(session,myAccountEmail,recepient,order);
    Transport.send(message);
    System.out.println("Message Sent successfully");
}

private static Message prepareMessage(Session session,String from,String to,String orderInfo) {
    Message message = new MimeMessage(session);
    try {
        
        message.setFrom(new InternetAddress(from));
        message.setRecipient(Message.RecipientType.TO, new InternetAddress(to));a
        message.setSubject("Your subject here");
        message.setText(");
        return message;
    } catch (AddressException e) {
        e.printStackTrace();
    } catch (Exception e) {
        e.printStackTrace();
    }
    return null;
}

}

Now that you can no longer use login and password with Googles smtp server the only option really is to use XOauth2

I havent used Jakarta before but it appears to support it. You should look into OAuth2 Support

Properties props = new Properties();
props.put("mail.imap.ssl.enable", "true"); // required for Gmail
props.put("mail.imap.auth.mechanisms", "XOAUTH2");
Session session = Session.getInstance(props);
Store store = session.getStore("imap");
store.connect("imap.gmail.com", username, oauth2_access_token);

Apps password

option two is to go to your google account and generate an apps password

When running your code use the password generated instead of the actual users password. The main issue with this being there is no telling how long google will continue to support apps password.

To those who followed the other answers but are still getting the "Authentication Failed" error when using an app password, a key point is that this solution is NOT working for XOAUTH2 if you are using that or are following a guide saying to use oauth2.

So in the following code:

props.put("mail.imap.auth.mechanisms", "XOAUTH2");

Simply change it to the following:

props.put("mail.imap.auth.mechanisms", "XOAUTH");

and it should work, keeping all else the same.