PhpBB3 Why can't activation emails be sent from the mobile version?

Question

Email

on a separate subdomain there is a version of the forum with a design for mobile
index.php of this subdomain sets a constant and redirects to the main folder of the forum where the design and other minor changes are selected by this constant the only mail-related change in $config['server_name'] I checked for sending not for some reason, activation letters are sent from the full version, but not from the mobile
define('IS_MOBILE', true);

Answer 1

figured out
the subdomains in httpd.conf have different mail settings