Makes sense, thank you.
Years ago, I didn't understand that pixel thing. It finally clicked when I read some article saying that if you choose not to load images in your email, you will not load the pixel. If your images load by default, you are effectively sending out a read receipt to anyone who put an image in that email, and a beacon pixel in that image. You can tell I'm really tech savvy.
Protonmail does not load images by default.