An email score is a number from 0 to 10 that indicates the quality of the email
An email with a score of 0 is surely spam while an email with a score of 10 si genuine.
To get a score of 10 if you have your own infrastructure, you should follow this configuration.
http://www.mail-tester.com/ is a website that calculate a score
You can also test your email infrastructure by checking the test of your email provider. See Email - How to test if your server email configuration was done correctly ?