Ah, but Clova handles that. It locks to the domain, not the sender or the subdomain. So both your examples would still be allowed (citi.com and bankofamerica.com). There are also permanent inboxes in the system, which allow anyone. The trick is to delete them after a while when they get polluted with spam.
banks also often have multiple domains - different one for transactional emails, different one for statements etc.
Instead of auto-locking it should be possible as user to configure the list of allowed domains that land there.
I have had banks using different domains totally, like bank.com and bank.email and notifications.bank.com etc.
And then you have India where every bank domain is required to end in .bank.in