How Limits Work

Limits Hierarchy

You can specify limits on outgoing mail at the following levels: Mail server > service plan > subscription > domain and mailbox.

The limits that you specify in Server-Wide Mail Server Settings act as defaults for Plesk objects at all lower levels of hierarchy. However, if you set custom limits at some level of hierarchy, then these custom limits will act as defaults for lower levels. For example, if you set custom limits for a service plan, the plan’s limits act as defaults for subscriptions created under this plan. Similarly, a subscription’s custom limits act as defaults for its domains and mailboxes.

The values of custom limits can be greater than the default values.

Customers can change their limits only at the domain and mailbox levels.

How Limits Work

The number of outgoing email messages sent from a parent object (such as a subscription) is counted as the sum of email messages from its child objects (such as domains). Therefore, limits work in the following way:

  • The sum of messages from all domains of a subscription cannot be greater than the subscription’s limit.
  • The sum of messages from all mailboxes of a domain cannot be greater than the domain’s limit.


The limit of a parent object is more important than individual limits of child objects. For example, if the limit for a subscription is reached, no domains of this subscription can send mail, even when some of the domains have not yet reached their individual limit. Similarly, if the limit for a domain is reached, no mailboxes of this domain can send mail, regardless of the fact that some of the mailboxes have not reached their individual limit.

If a user or a script sends an email message by 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 for a subscription.