I just heard from a classmate that they did not receive notifications when there was a message waiting for them at the class website. Evidently, they hadn't visited the site in a while and had a message from a friend dated two months ago. I just assumed that because I received notifications of new messages, they did too.
I'm not sure how to direct them to receive notifications of messages... or even if they can since they aren't an administrator. Could you tell me how they can change their notifications setting to notify them of a new message at the class website?
Thanks.

It might be that the email went into the junk email. Or that there was just a malfunction that day. Maybe send an email to that classmate to see if they recieve a notice this time. Otherwise I have no suggestions. Good luck.

Make sure that Classmate has whitelisted postmaster@classcreator.net. Try clicking on your Email The Class link and email just that individual Classmate again. See if they get the notice. We actualy switched to a completely different email system a few days ago, so this will be a brand new test. I expect them to get the notice, but if they don't let me know.

Isn't there also a mechanism by which an individual can opt out of receiving e-mail from the site? Has that happened in this case?

I'm glad you said that. Yes. If a Classmate opts out from the bottom of any email message (sometimes accidentally) a new field will appear in their Details area called "Receive Emails." And it will be set to "No. You can set it back to Yes to fix the problem.