Debug PHP spam mails

touch /var/log/mail_php.log
chmod 777 /var/log/mail_php.log

vi sendmail-wrapper.sh
#!/bin/sh
logger -p mail.info sendmail-wrapper.sh: \
site=${HTTP_HOST}, \
client=${REMOTE_ADDR}, \
script=${SCRIPT_NAME}, \
pwd=${PWD}, \
uid=${UID}, \
user=$(whoami)
/usr/sbin/sendmail -t -i $*

chmod +x /usr/local/bin/sendmail-wrapper.sh

then
vi /usr/local/bin/env.php

chmod +x /usr/local/bin/env.php

in global /etc/cl.selector/global_php.ini and /opt/alt/php*/etc/php.ini
mail.add_x_header = On
sendmail_path = /usr/local/bin/sendmail-wrapper.sh
auto_prepend_file = /usr/local/bin/env.php

cagefsctl --rebuild-alt-php-ini

addded
/usr/local/bin/env.php, /usr/local/bin/sendmail-wrapper.sh,
to /etc/cagefs/conf.d/php.cfg