SMTP Port: 587 (or 465 using SSL encryption)
Username: Your Gmail account email address (e.g. [email protected])
Password: Your Gmail account password
You need to input the above details into the YaySMTP settings area accordingly, then enable less secure apps in Gmail or G Suite by logging into your Gmail or G Suite account and then open "less secure apps" or click hereand and switch ON the toggle. Mind you, if 2-Factor Authentication is enabled for your account, you will need to disable it before enabling this toggle.
Sometimes you could get notification from Google warning you about suspicious activity in your account, you can click Check activity and follow the instruction to mark it as safe.
Just make sure you click save in the YaySMTP settings to save your details and that's all.
Now you have successfully integrate Gmail SMTP server into your WordPress site!