I appreciate your instructions. I have learned much about this plugin.
But, I still have the same problem. My original question. The e-mail notice I receive when someone signs up is so unreliable. The other day, I finally got the notice on someone who had sign up, and has been on my list, for months. Also, one person who is already on the list, for whom I have never received the notice by e-mail. I am talking about the e-mail "I" receive when someone signs up with subscription. I am not referring to the sign up through commenting. I only have Jetpack for e-mail subscription. No other plugin. Lastly, there was one notice I received, for which no one seems to be listed.
Is this a bug? Is it OK to leave it alone like this?
I would appreciate for advice.