In my test, even if the customer doesn’t have login/access to the NetSuite account, you can still set them as your recipients in Saved Search.
To do this:
1. Open the Saved Search created to be sent to your customers
2. In the email tab, specify the Recipients
You can also set the frequency of the email notification, or the saved search email will trigger all updates (see Send email alerts when records are created/updated) or scheduled (Send emails according to schedule).
Once triggered, an email notification will be sent to the customer even if they don’t have access to the account.