Task Assignment Email Notification
There are currently no email alerts in Taskfeed. This is by design. The goal was to reduce email. Some people do still like to receive notification when Tasks are assigned. For Salesforce Enterprise and Unlimited customers this is possible using workflow. For Professional Edition users this is not possible. Consider building these notifications into Taskfeed and make them optional for users.
Released in Taskfeed 8 you can now manage your own notification settings. Choose to be notified in-app or by email.