When you sign up for ipipi, you enter an email address that you would like ipipi to use to communicate with you. You can register many email accounts with ipipi, such as those you use for your forwarding rules, but one email address is always left as default.
If you ever change your email or would like another email to be your default email address connected to your account, simply follow these instructions:
1. Log in to http://www.ipipi.com
2. Under "Settings->Registered Devices" click on "Add E-mail"
3. Enter in your new email address
4. Check that email address for your confirmation code (leave this browser open while you do so)
5. Enter your confirmation code in the box
6. Return to the "Registered Devices" screen and click on your new email address
7. Check the box indicating you would like this email to become your default