Notify On Error can be found under Account Settings Tab. Here you can specify the email or emails that will be used to receive notifications in case of any errors that might arise in the application. This includes any errors that happen when merging a document/data route or processing a delivery of a document. You can add multiple emails by separating them with comma:
Notify On Error
The Account Settings tab provides options for managing your account, including updating the account name, managing members and roles, and handling Formstack document migrations.