This contribs allow you to redirect php generated emails to qpsmtpd instead of qmail. Doing so, you will be able to filter those generated emails as those were generated by a regular SME user, and you will be able to have them DKIM signed if this is enabled.
yum install smeserver-sendmail-wrapper --enablerepo=smecontribs
then if you only have the base php
expand-template /etc/php.ini service httpd-e-smith restart config set UnsavedChanges no
if you have smeserver-php-scl installed, just do :
signal-event php-update config set UnsavedChanges no
if you want to disable the sendmail wrapper for the core php :
config setprop php sendmail disabled expand-template /etc/php.ini service httpd-e-smith restart
to enable again
config delprop php sendmail expand-template /etc/php.ini service httpd-e-smith restart
You can do the same using the php scl version, e.g. for php70
config setprop php70 sendmail disabled signal-event php-update
yum remove smeserver-sendmail-wrapper
Only versions released in smecontrib are listed here.