An update; I have discovered something new. My ISP is Earthlink and I've been using my Earthlink email address in my Computer Hope Profile ever since I joined the forum. Last night, I changed the email address in my Profile to a WebMail account - entirely separate from Earthlink - that I seldom use. Today, email notifications came through to that address.
I don't view this as a solution because I definitely prefer to use my Earthlink email address and download POP mail to my computer, as usual. I'm having no problem receiving mail from any other sender. I just changed the email address in my Profile back to Earthlink just to see whether the process of resetting causes it to work again.
By the way, I called Earthlink support 2 or 3 days ago to discuss this. They suggested lowering my spamBlocker setting, at least temporarily, to see whether that would affect this. I had it set to the highest level; I lowered it to the lowest level, which negates the spam blocking but I was willing to do this as a troubleshooting step. I still did not receive CH notifications.
I'm wondering whether Earthlink is blocking CH email notifications in a pre-screening process. I believe they filter out some mail and do not allow it to flow through to any of their users, regardless of the spamBlocker setting used by individual users. For example, with my former ISP - going back some years - I received unsolicited pornographic email. Once I switched to Earthlink, that stopped completely and never resumed, even though I did not use the spamBlocker feature for quite awhile with my Earthlink account. Clearly, Earthlink just filters that type of mail from all users, except, I presume, where the user has specifically subsribed to such mail.
What I wish CH admin would do is verify whether all mail going to Earthlink users is getting blocked. I believe that would not be too difficult. Non-delivery notices should be coming to CH, right? If I can get confirmation that this is happening, then I can call Earthlink Support again and discuss the exact cause of the problem.