Change of e-mail content

Hello, I would like to know if it is possible to modify the master file of mail.blade.php (I can't find it), so that I change some things in the header and footer.

What I am trying to do is change the name of the sender in the email header and footer from Akaunting to "OneInterWeb Support". I am aware of the APP_NAME variable and I tried to change it but it doesn't work.

Here is a photo: https://ibb.co/cvAPjo