To change your email preferences, go here → Email Settings → toggle the Monthly Product Updates button to subscribe or unsubscribe.
Alternatively, click on your avatar (upper-right corner of the screen) → Account Settings → Email Settings → toggle the Monthly Product Updates button to subscribe or unsubscribe.
To subscribe / unsubscribe from board comment notifications via email, open the board, click on the comment icon → Comment Settings → check / uncheck Receive Notifications for All Comments:
Unsubscribe from Card Notifications
If you're getting email notifications about cards, open or select the card and then click the eye icon to unwatch: