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 you profile page
2) Click "Profile" button
3) Click "Settings" button
4) Turn-on/turn-off "Session Summary E-mail" option