Yeah, NetSuite emails don't trigger OOO replies because they usually come from a noreply address or system email that Exchange treats as automated. Most teams just live with this limitation since it's pretty minor. If it's really important, you could customize outbound emails to use actual user email addresses as the sender, but that creates other authentication headaches. Alternative is adding an auto-signature to NetSuite emails mentioning when someone's out, but that's manual management.