If you are getting the above issue while setting up google / gmail SMTP server. You need to follow below steps it will surely solve your problem. I had also faced this issue and following the below steps resolved my problem and mail getting started to come in my inbox.
1- You need to enable 2 step verification in your google account setting
2- Now create App password which you will need to use in your website
3- Choose "Custom Name" and click to generate
4- Go to your laravel .env file and update below details:
MAIL_PASSWORD=password (Which you just generated it)
5- Now restart your apache server
These are the steps you need to go through and it will solve your problem without any headache.