How to limit the number of emails sent through PHP scripts?
The number of outgoing emails sent by the Linux Sendmail utility can be limited as usual emails, however some specificity take place.
If a user or a script sends an email message using the Linux Sendmail utility, then Plesk counts this outgoing message for the corresponding domain in case the script is handled by mod_apache (mod_php, mod_perl, mod_python, and so on). In other cases (CGI, FastCGI), Plesk counts the outgoing message for the corresponding subscription, but does not count it for the corresponding domain.
A script or a user can send messages using Sendmail, if the option Allow scripts and users to use Sendmail is switched on in Plesk at Tools & Settings > Mail Server Settings.
To limit the number of these emails, configure limitations on outgoing emails on a subscription level.