On the 'Email Notification Preferences' Page inside your User Control Panel you can set up, what type of Email Notifications you want to receive.
Turn off notifications - This Options turns off all Notifications and you won’t receive any emails.
Notification for all posts on all Questions - You will receive Instant Email Notifications when someone has posted a new Message.
Notification for Questions you've posted to, watched or marked as favorite - You will receive Instant Email Notifications when someone has posted a new Message in a Question, you have posted before, a Question you watch, marked as favorite, or a forum.
Notification for Questions or forums you've selectively watched (listed below) - You will receive Instant Email Notifications when someone has posted a new Message in a Question or forum you have selected to watch (See List Below).
Receive once daily digest/summary of activity? - If this Function is enabled you can turn this option on to get an Email with all new Activities about Questions and messages from current day as daily digest (summary) in one mail
Receive an email notification when you get a new private message? - You can also turn on/off Email Notifications when you receive a private message.