That certainly isn't an issue on mine, so it must be a bug/glitch.
I can add new email addresses to the address book on our WorkCentre 5890, delete addresses etc. Some email addresses can be added to the email favorites, but not those with a dot in the address. For example, firstl@example.com can be added fine, but first.last@example.com will not be added to the email favorites. I can click "email favorites" and then save, but the address will not be in the list of favorites.
Thank you in advance for your help!