To change your email delivery option, you must first sign in to the Google Account associated with the email address subscribed to the group, then please follow these steps:

1. Visit the Google Groups homepage when in your email 
2. Click on "My Groups"
3. Choose the email delivery option that you prefer for your group from the drop-down menu and save your change 

• Don’t send email updates
• Send daily summaries 
• Send combined updates (25 messages per email)
• Send me an email for every new message (about 3 per) 

       http://support.google.com/groups/answer/46605?hl=en