Make sure email configuration is correctly setup. The email configuration is setup under Preferences > Settings > Email. Leave SMTP Server, Port Account Name, and Account Password blank for now.
Please refer to the chapter for more information on email settings : Ch. 006. Email Settings
2. Make sure your User account has Receive Notifications checked.
3. Check that the Group name you are sending email to is listed correctly in Email Notifications. The Group may have been renamed and as a result, the email is trying to send to a Group that no longer exists. In Email Notifications > Select Message > Customize this message. The Users list contains the current list of available Groups. Compare the Group name in the "Who receives this notification" list with the Group name in the Users list. If they are not exactly the same,replace the Group in the "Who receives this notification" list with the appropriate Group from the Users list.