So do I. And then they say, "You're right - I didn't check my email today!"
And then we got through the same thing the next day. And the next day. And the next.
We all have those
What if you walked into their office every time you receive an email from them acknowledging you received it and its on your to-do list, then again a few minutes later to let them know it reached the top of your list and are ready to start working on it, then again when you take a coffee break, then again when you respond.. You get my point.
It may be annoying for the first few times, but hopefully the person will realize what's going on.