What is the cause of the error when trying to send an email from a form (PHPMailer)?

Question

PHP

Hello!
Please help me solve the problem:
I'm trying to set up sending emails to email from a local server (XAMPP Version: 8.0.2). Yandex SMPT is configured, previously connected another mail.php from this address without a handler, everything worked.
I hope for your help.

HTML submission form:

js handler:

mail.php file:

When trying to send a letter, the following errors come out:
In the console:
VM426:1 Uncaught (in promise) SyntaxError: Unexpected token < in JSON at position 0

"Sources" tab:

<br />
<b>Fatal error</b>:  Uncaught PHPMailer\PHPMailer\Exception: Невозможно запустить функцию mail(). in C:\xampp\htdocs\testform2\PHPMailer\src\PHPMailer.php:1904
Stack trace:
#0 C:\xampp\htdocs\testform2\PHPMailer\src\PHPMailer.php(1637): PHPMailer\PHPMailer\PHPMailer-&gt;mailSend('Date: Fri, 7 Ma...', '&lt;h1&gt;\xD0\xB2\xD0\xB0\xD0\xBC \xD0\xBF\xD1\x80...')
#1 C:\xampp\htdocs\testform2\PHPMailer\src\PHPMailer.php(1468): PHPMailer\PHPMailer\PHPMailer-&gt;postSend()
#2 C:\xampp\htdocs\testform2\mail.php(35): PHPMailer\PHPMailer\PHPMailer-&gt;send()
#3 {main}
  thrown in <b>C:\xampp\htdocs\testform2\PHPMailer\src\PHPMailer.php</b> on line <b>1904</b><br />

Screenshots of lines in phpmailer.php referenced by console

Answer 1

The mail() function is not allowed on the hosting or sendmail/postfix/exim is not installed.
The solution is to use sending via SMTP.
Invalid JSON is returned back to the browser - the error text comes.