Plesk server preferences and global mail service settings are held by the prefs node. The node is presented by complex type serverPrefs (plesk_server.xsd) and structured as follows:

• The max_connections node is optional. It sets the global mail service limitation - for Courier-IMAP, it sets the maximum number of IMAP or POP3 processes that can be started on the server. For Dovecot - it sets the maximum number of mail users that can be logged in at the same time.
• The max_connections_per_ip node is optional. It sets the global mail service limitation - the maximum number of POP3/IMAP connections allowed from the same IP address.
• The outgoing_email_mode node is optional. It specifies which IP addresses should be used for sending email. It can take either of the following values:
  • domain-ip - mail is sent from domains’ IP addresses
  • domain-name - mail is sent from domains’ IP addresses with an SMTP greeting
  • explicit-ip - mail is sent from a specified IPv4 or IPv6 address. The addresses are specified by means of the options outgoing_email_mode_explicit_ipv4 and outgoing_email_mode_explicit_ipv6. When this mode is selected, all domains’ DNS zones are configured to use the specified IP addresses for A and AAAA records to which MX records refer.
• The outgoing_antispam node is optional. It switches on or off the server-wide limitation of outgoing messages per hour.
• The outgoing_messages_mbox_limit node is optional. It sets an hourly limit on the number of email messages that can be sent from a mailbox.
• The outgoing_messages_domain_limit node is optional. It sets an hourly limit on the number of email messages that can be sent from all mailboxes under a domain.
• The outgoing_messages_subscription_limit node is optional. It sets an hourly limit on the number of email messages that can be sent from all mailboxes under a subscription.
• The enable_sendmail node is optional. It specifies whether scripts and users are allowed to send email messages (on behalf of the subscription’s system user) by using Sendmail even if the limits for a mailbox and domain are exceeded. The maximum number of messages that can be sent through Sendmail will be defined by the limit for an entire subscription.
• The report_period node is optional. It specifies a period - 1 day (P1D), 1 week (P1W), 2 weeks (P2W), 1 month (P1M). If there were attempts to exceed the limits on outgoing mail during that period, the Plesk Home page displays an alert. Also, reports are created based on the statistics for this period by default.
• The notification_period node is optional. It specifies how often the server administrator should be notified about attempts to exceed outgoing mail limitations during the specified report_period. Available values are: 15 minutes (PT15M), 1 hour (PT1H), 6 hours (PT6H), 12 hours (PT12H), 1 day (P1D).
• The stat_ttl node is optional. It specifies the time-to-live of server traffic statistics. Data type: integer.
• The include_remote_databases node is optional. It specifies whether to include the remote Microsoft SQL databases into disk space usage calculation. Data type: boolean.
• The traffic_accounting node is optional. It specifies the traffic accounting type. Data type: integer. Allowed values: 1 (only inbound) | 2 (only outbound) | 3 (inbound & outbound).
• The restart_apache_interval node is optional. It specifies the Apache restart interval (in seconds) - the number of seconds after which Apache should be restarted. Data type: integer. Supported only in Plesk for Linux.
• The apache_pipelog node is optional. It specifies whether the Apache logs piping is turned on or off. Data type: boolean. Supported only in Plesk for Linux.
• The ftp-over-ssl node is optional. It specifies the type of connections from external FTP client that the Plesk FTP server should allow. Data type: string. Allowed values: disabled (only non-secure FTP connections are allowed) | enabled (both secure FTPS and non-secure FTP connections are allowed) | required (only secure FTPS connections using SSL/TLS protocol are allowed).
• The mail_notifications node is optional. It specifies whether Plesk is allowed to send email notifications through the external SMTP server specified with smtp_host node. Data type: boolean.
• The smtp_use_default_settings node is optional. It switches on or off an internal Plesk mail account for sending Plesk notifications when the relay is closed for the local host.
• The smtp_host node is optional. It specifies the host name or IP address of the external SMTP server for outgoing mail. Data type: string.
• The smtp_port node is optional. It specifies the port for the external SMTP server for outgoing mail. Data type: integer.
• The smtp_login node is optional. It specifies the username for accessing the external SMTP server. Data type: string.
• The smtp_password node is optional. It specifies the password for accessing the external SMTP server. Data type: string.
• The smtp_tls node is optional. It specifies whether the external SMTP server requires secure FTPS connections. Data type: boolean.
• The smtp_allow_users node is optional. It specifies whether hosted users’ scripts are allowed to send outgoing mail through the external SMTP server. Data type: boolean.
• The aps-force-updates node is optional. It specifies whether the force applications updates are turned on. Data type: boolean.
• The aps-suggest-updates node is optional. It specifies whether the automatic updates should be turned on by default for newly installed aps. Data type: boolean.
• The preview-protection (Windows only) node is optional. It specifies whether the website preview mode should be available to users. Data type: boolean.
• The waf-rule-engine node is optional. It switches the web application firewall server-wide to either of the following modes: on, off, detection-only.
• The waf-rule-set node is optional. It specifies the rule set that should be used by the web application firewall. Supported values: tortix (Atomic ModSecurity rule set) and crs (OWASP ModSecurity core rule set).