Why might mail() not work?

Question

PHP

Why might the php mail() function not work?
server on centos, msmtp installed, exchange mail server, PHP 5.6.33
when sent from console with
echo "Testing" | mail -s "Test" [email protected]
php -r "mail('[email protected]', 'Test', 'Test');"
both letters reach, when sending from the site, nothing is written to the log;
verification of sending from the site is performed by such a file

$sender = '[email protected]';
$recipient = '[email protected]';

$subject = "php mail test";
$message = "php test message";
$headers = 'From:' . $sender;

if (mail($recipient, $subject, $message, $headers))
{
    echo "Message accepted";
}
else
{
    echo "Error: Message not accepted";
}

did not find anything in .htaccess, where to dig?

Answer 1

I'm dumb.
due to the fact that the site runs under the apache user, and I made the config under root,
you need to override sendmail_path = msmtp -C /home/msmtp/.msmtprc -t -i
copy the finished config /root/.msmtprc to /home/msmtp/. msmtprc and make the file owned by apache with permissions 600