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
Documentation / Reference
- Spam score spam score