Custom Limits

To protect from threats of the three types described in Protection from
Outbound Spam, you can keep the default limits (which are
specified in Mail Server Settings) or you can set up custom limits
at the corresponding levels of Plesk objects (service plan,
subscription, domain, and mailbox).

If you think that certain threats are unlikely, then you can set the
Unlimited value for the corresponding Plesk objects. To turn off the
protection for a subscription, set the Unlimited value at all the
three levels – a subscription, domains under this subscription, and
mailboxes on the domains. On the other hand, to prohibit sending mail
altogether, set the 0 value for the limits.

To learn more about custom limits, see How Limits Work.

Setting Custom Limits for Service Plans

To set up limits on the number of outgoing email messages for a
service plan:

Go to Service Plans > select a plan > the Mail section and edit
the settings:

• Outgoing messages from a mailbox (per hour). Sets up a custom
  limit on the number of outgoing email messages from a mailbox. This
  limit will be used by default on mailboxes of the plan’s
  subscriptions.
• Outgoing messages from a domain (per hour). Sets up a custom
  limit on the number of outgoing email messages from a domain. This
  limit will be used by default on domains of the plan’s subscriptions.
• Outgoing messages from a subscription (per hour). Sets up a
  custom limit on the number of outgoing email messages from a
  subscription. This limit will be used by default on the plan’s
  subscriptions.
• Allow system users and scripts to use Sendmail (Linux only). The
  system users of the plan’s subscriptions will be able to send email
  messages by using Sendmail even if the limits for a mailbox and
  domain are exceeded. The maximum number of messages that scripts can
  send will be defined by the limit for a corresponding subscription.
  Users can use Sendmail through SSH on behalf of a subscription’s
  system user.