How to disable PHP mail() function for a spamming domain on Plesk for Linux server?

To disable PHP mail() function for a domain, follow the steps below:

1. Log into Plesk

2. Go to Subscriptions > example.com > Customize > PHP settings

3. Add disable_functions = mail string to the Additional configuration directives field

    

4. Click OK button to apply changes

Note: Make sure that the corresponding subscription is locked, otherwise the global definitions of that subscription plan will be synced and domain's specific configuration will be lost.

Warning: If disable_functions = mail is set, but 'mail' is not listed as disabled in Domains > example.com > PHP Settings > phpinfo (), check if some additional PHP modules are installed on the server. Additional PHP modules can overwrite php.ini settings for the domain.

In case Suhosin PHP module is installed, follow these steps:

1. Connect to the server via SSH and comment out disable_functions directive in Suhosin config in order not to override the same directives in domains php.ini.

   # grep disable_function /etc/php.d/suhosin.ini
   ;disable_functions =

2. Add additional PHP directive for domain:

   disable_functions = exec, system, mail

Note: If mail() function is disabled for PHP, but emails are still being sent by unidentified script, sendmail can be disabled completely.

Usage of sendmail utility can be disabled server-wide with the settings at:

Home > Tools & Settings > Mail Server Settings (option: Allow scripts and users to use Sendmail).

Or on service plan at:

Home > Service Plans > <service_plan_name> > Mail (option: Allow scripts and users to use Sendmail).

Or for the subscription at:

Home > Subscriptions > example.com > Outgoing mail control > Subscription > Change limits (option: Allow scripts and users to use Sendmail).