“From” e-Mail address + upload file format issue

Hi, I have the following issues:

Within the administration e-mail settings the field “from”-e-Mail address is highlighted in red and I don’t understand why. It’s been automatically filled with “[email protected]” – and sending test messages works – they’re coming from said e-Mail address. So why is that field still red?

Furthermore, regarding file upload: how do I need to format the accepted file formats? Seperated by spaces or commas or something else?
I tried the following so far, neither worked:
.pdf .jpg .jpeg .png
.pdf, .jpg, .jpeg, .png

Thanks for getting back!