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

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Mikhail Shport
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Plesk for Linux kb: how-to ABT: Group A

Applicable to:

  • Plesk for Linux

Question

  • How to disable mail() function for a spamming domain on the Plesk server?

Answer

Disable mail() function for a subscription via GUI

  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:

    php_add.png

  4. Click OK button to apply changes

Warning: Make sure that the corresponding subscription is Locked and does not sync with its Service Plan. Otherwise, the changes will be rewritten by the values defined in the Service Plan.

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 the 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:

    CONFIG_TEXT: disable_functions = exec, system, mail

Disable mail() function for a subscription via CLI:

  1. Connect to the server via SSH

  2. Execute the following command:

    # plesk bin subscription_settings -u example.com -outgoing_messages_enable_sendmail false

 

Also, the Sendmail utility might be disabled completely to disable the functionality of sending such emails completely:

Disable Sendmail utility completely

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

  • Log in to Plesk GUI > Tools & Settings > Mail Server Settings > Disable the option Allow scripts and users to use Sendmail

Or on the Service Plan level:

  • Log in to Plesk GUI > Service Plans > <service_plan_name> > Mail > Disable the option Allow scripts and users to use Sendmail

Or on the Subscription level:

  • Log in to Plesk GUI > Subscriptions > example.com > Outgoing mail control > Subscription > Change limits > Disable the option Allow scripts and users to use Sendmail

Additional Information

Also, it is possible to block all outgoing mail that is being sent by PHP scripts like PHPMailer by adding the following iptables rule (on RHEL/CentOS):

  1. Connect to the server via SSH
  2. Save the current iptables rules to the file:

    # iptables-save > /root/pre_iptables_rules

  3. Add the rule that blocks all outgoing packets send by processes where the owner is not postfix excluding local connections from Webmail:

    # iptables -I OUTPUT -m owner ! --uid-owner postfix -m tcp -p tcp --dport 25 ! -d 127.0.0.1 -j REJECT

  4. Install and enable necessary package:

    # yum install iptables-services && systemctl enable iptables-services

  5.  Save iptables rules to make the changes permanent:

    # /sbin/service iptables save

Comments

2 comments

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  • Avatar
    Arvind Kumar Madhukar

    Thanks for the great article but it is not working in my case,

    Hi Marc Vidal

    I have already disabled the function Mail () from the PHP setting of a wide server, still, I can see that the user is able to send mail from the server to outside.

     

    the typical things is here i have also disabled the mail service from the panel for this domain as well there is no mail id still user able to send mail from Plesk default user.

     

    Please suggest on this, which is helpful

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  • Avatar
    Anton Maslov

    Hello Arvind,

    Steps described in this article allows fully block mail. If users still can send that it is probably not fully applies or something else. Nevertheless to check the issue it is required to create ticket as it is not something that can be simple advised in comments:

    https://support.plesk.com/hc/en-us/articles/213608509-How-to-submit-a-request-to-Plesk-support-

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