Email notification settings are set per user through the main page of My PBworks.

https://my.pbworks.com

You'll be presented with a list of the workspaces you're a part of.  Next to each workspace listed, you'll see a checkbox which allows you to enable or disable notifications for any workspace you are a part of.  By unchecking the checkbox next to the workspace, you will disable notifications for that particular workspace.

To change the frequency of notifications being sent to you,  you must first log in to my.pbworks.com.  Then, at the bottom of the page, you'll see the following drop-down list which allows you to set the frequency of your notifications.   Click the "Submit" button under the dropdown box to set your preference.