After your sessions with English Ninjas tutors., all of your messages in the session, and tutor's review about your skills are send to you with an e-mail.
It is not compulsory but by default it comes with turned-on.
If you don't want to get session summary emails you have to turn-off "Session Summary Mail" option.
In order to change this option
1) Go to your profile page and push "Settings"
2) Turn-on / turn-off "Session Summary E-mails" option