You should be able to change or add email addresses here:

1.  Customers > Customer Center

2.  Double-click on the customer whose emails address you want to add to or change

3.  On the Address Info tab you will see fields for main email and cc email (to the right).  Enter any email addresses that you want there.  We have found an issue w/QB if you are using multiple emails do not enter a space after the ; symbol that you use to separate the email addresses.  If you use a space it will tell you it could not send.  so example:  [email address removed];[email address removed]

4.  Click OK and it should save them there.