Why doesn't location work?

Question

Nginx

Please tell me how to set up such a location, this example does not work.
When typing the address
http://sites/mail
In the address bar of the browser, the path changes to sites/mail, but index.php does not start,
writes File not found .
If you just type the address, then index.php from /var/www/html works

server{	
  ...	
  root /var/www/html;
  index index.php;
  
  location  /mail {	
  return 301 http://sites/mail;
  }
    
  location / {
    rewrite ^/([^\.]+)$ /$1.php ;
  }
}

There are two directories (two sites: html and mail) and each has an index.php, what is the correct way to run index.php from the mail directory?

Answer 1

location  /mail {	
  return 301 http://sites/mail;
  }

And what do you think this location should do? When they go to /mail, again send to /mail?