Who can receive email notifications?

For events like failed file existence, data errors or success/failure, it looks as though I can set up email messages only for Celigo customer accounts. How do we notify other business process owners (BPOs) from within a flow?

The list of recipients is indeed limited to integrator.io account email addresses. 

If your concern is for licensing or allowing others to modify integrations, one option is to add stakeholder accounts with Monitor-level access. Then, they can subscribe to email notifications without changing the flow.

Another solution within integrator.io is simply to provide a group alias for your account’s email address.

Alternatively, you could consider configuring automatic email forwarding from the notified account, based on text filters in the integrator.io email.