Thank you for your speedy reply!
Sadly Plesks mail limit options for hosts doesn't work for PHP mail from clients sites, only authenticated user email accounts are counted and that system works brilliantly. If you could develop a way to alert admins of a configured volume of PHP mail would be...
I've got an issue with a couple of problem hosts on a shared Plesk box with PHP mail not being seen as part of the hosts outgoing send limits (as it would suspend and email alert me).
Does Mail-Log extension show the PHP generated emails? Are you able to search/filter for them? Is it possible...