Really?
Really?
In a way, you're not speaking the same language. Try assuming your clients have no concept of not just programming, but any of the process of building an application or solution to a problem that uses technology. Don't discuss details. They are probably paying you so that they don't have to worry about the details.
By way of example: I have the reverse problem with my wife. She is a nurse. When telling me about her day, she used to fly through a great deal of technical details using an amazing number of acronyms and abbreviations that I found not just unintuitive, but completely incomprehensible. I genuinely care about how her day was, but I found myself exclaiming in exasperation, "I have a clue what any of that means!" She now explains only what is necessary to get the point across, and defines acronyms as she goes along, if necessary. That works, but, in your situation, I'd abstract my communication at least one more level than that.
As soon as the client feels like he doesn't understand what you are saying, you stop becoming a problem-solver and start becoming a problem. In addition to whatever responsibilities he has on his end, now he needs to try to figure out what you are saying. The key to a happy client is removing problems from their plate.
Here's a different way to communicate the same things as your original email:
$CLIENT, you mentioned that you wanted a few changes
to the content of the site. If the changes are easy
to describe, you can just email them to me and I will
take care of it. Otherwise let's sit down/have a
phone call about the changes.
I've also done some research into the digital
signage that we discussed. I found an option that
will cost $30-$40 per sign, is that within your
budget? I can present all the options I've found
at our next meeting.
Notice that I tried to avoid any deep technical details (e.g. after you email me the changes, I will add an item to the bug tracker and do feature-branching to implement the changes then deploy to the staging server). My version is not perfect either, but I think it would be better received.An easy thing nerdfiles could have done was to attach the email in question. In that situation, there's no need for the client to dig through their emails to find something they may or may not have deleted, may have ignored, or had end up in their junk folder. Then you can trade out "If you did not receive it, please let me know" with "I've attached it for your convenience".