So what's the point in putting your e-mail address at the end of the license/about/readme ?
If you don't want to receive e-mails, don't put your e-mail.
If you just want to receive some kind of e-mails (like just congrats but not bugs), add that information in the end. Of course some people won't comply, but that's just human behavoir.
Now, just putting your e-mail and letting the black hole eat them without an answer is very disappointing to those who took their time to read the license/about/readme, find your e-mail, put their hope that you're able to help them in some problem, and then... nothing.
Edit
Yes, I did read the thread, the original post, and so on. I'm just putting myself in the position of the average costumer, or not-so-average, that took time to read the available documentation and tried to fix something, or to ask for a new feature, or anything else. He isn't receiving spam. I'm not suggesting, either, that he should address the problem or even find out who's the correct person to blame inside the company X that did the GUI of the radio for the company Y that finaly sold it to DENSO that will sell it to Toyota...
One way to fix would be, for example, changing the license in any future version to read "If you're using this software inside any component that will be used in a car, you should display the Copyright_automotive.txt contents instead of this one".
Edit 2
As far as I could find (in https://curl.haxx.se/docs/copyright.html), I would never blame regular car users, not even some tech users, if they couldn't find what Daniel is responsible for. The license just says:
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COPYRIGHT AND PERMISSION NOTICE
Copyright (c) 1996 - 2016, Daniel Stenberg, daniel@haxx.se, and many contributors, see the THANKS file.
All rights reserved.
Permission to use, copy, modify, and distribute this software for any purpose with or without fee is hereby granted, provided that the above copyright notice and this permission notice appear in all copies.
THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT OF THIRD PARTY RIGHTS. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
Except as contained in this notice, the name of a copyright holder shall not be used in advertising or otherwise to promote the sale, use or other dealings in this Software without prior written authorization of the copyright holder.
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If you read that and can find where it says that it's not about the GPS, the mapping of the Electronic Fuel Injection, the windshield wipers, or something else, or even that it's about some specific piece of software, please, just point it out.