The email address used to log in with will be the one that receives any and all submitted, accepted, rejected, submission failed, and related notifications to specific filings within the eFiling system. Because each of these types of notifications is specifically tied to the email address used to log in, there is not a way to add another email to these notifications. You may wish to change who receives the notifications by submitting envelopes under a different Firm User, but only their email address will receive those filing notifications.
This is, of course, separate from notifications of service, which are related to who is on the service list when a document is elected for service. Email addresses set up as Firm Service Contacts and attached to the case will receive service if a document is served and their service contact entry is checked to receive service.