I have got a website that was perfectly sending SMTP mail using the PEAR Mail package.

After I upgraded my domain to the PHP 8.1 version CGI, the function

`$smtp->send($to, $headers, $email_body);` stopped working!

Status code 500

the log file error is:
include\_once(Net/SMTP.php): Failed to open stream: No such file or directory in /home/......./pear/share/pear/Mail/smtp.php

Therefore I tried to install it but the error this time was:

pear/Net\_SMTP is already installed and is the same as the released version 1.10.0 install failed

and in the Chrome Developer Tools "network" response there is not a RESPONSE ! Empty!
Any idea?