Membership is FREE, giving all registered users unlimited access to every DNForum feature, resource, and tool! Optional membership upgrades unlock exclusive benefits like profile signatures with links, banner placements, appearances in the weekly newsletter, and much more - customized to your membership level!
I heard some complainings about enom's notification system before, too. If this is a system problem, they must fix it because this may cause big losses and big troubles for its customers.
Maybe it was caught as spam.
You should maintain a list of all your names and expiry dates. If you rely on courtesy reminders you are going to lose domains sooner or later.