The best way to approach these things, as always, is with humor.
Original Sender: Where are my files??????????
You, Possible Answer 01: I found them!!!!!!! They're inside the computer!!!!!
You, Possible Answer 02: I don't know?!?!?! Shall I help you find them?!?!?!
Zoolander jokes aside, I think if you responded to them with humor in kind (as you had done so here in your post), the other person would get the point.
For example, see this answer here, similar in that these are both addressing pet peeves.
(I only call this a pet peeve since it's something you feel personally. I am not passing judgment on whether it's warranted, though, for what it's worth, I do :).)
However, as you have posted Poe's Law, I would have to add that I would only advocate this solution for those with whom you have at least some rapport or those lateral or subordinate to you.
For those who are above you or who might not know not to take you seriously, I would just be frank and candid about it, using I-messages:
Hi, sorry, I found your files, but I just wanted to ask if you could please refrain from using so many question marks and exclamation marks in the future.
It feels a bit like yelling and even if you had not marked the question with so many question marks, I would have taken you seriously and dealt with the situation urgently.
Meanwhile, if you want to convey that this email is urgent, there is also the option to change the email's urgency to "High Priority," in which case, I'd get the same message.
Thanks and sorry for bothering you with this.
Whichever way you choose, owning the pet peeve and making it work for you by thanking the person and apologizing for inconveniencing them is the position of strength.
What do you think? Do either of these options work for you?
If it helps, I just used the second approach the other day with my own boss.
We have a good enough rapport that I hadn't needed to say so much and had only needed to state my request and it had been effective, but also, in part because I think that she herself was willing to acknowledge the request and make the change.