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.

Note: Depending on the mail server used by Plesk, some limits might not be applicable. Also, you cannot set limits if a remote mail server is used.

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.

Note: These limits are used as presets for newly created subscriptions. When you change the limits for a service plan, the changes are not applied to the subscriptions that are locked or that have the “Ability to change mail settings” permission.

Setting Custom Limits for Subscriptions

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

  1. Go to Subscriptions and click the subscription for which you want to change limits.
  2. Click Outgoing Mail Limits on the toolbar 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 the subscription’s mailboxes.
  • 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 the subscription’s domains.
  • 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 for the subscription.
  • Allow scripts and users to use Sendmail (Linux only). The system users of a subscription 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 the corresponding subscription. Users can use Sendmail through SSH on behalf of a subscription’s system user.

Note: When you change the limits for a subscription, it does not become locked and unsynced with the service plan.

Setting Custom Limits for Domains

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

  1. Go to Domains, select the domain for which you want to change the limit, and open its hosting settings in the Customer Panel.

  2. Go to the Mail > Mail Settings section and click Edit Limit next to the required domain in the list of domains.

    To set the same limit for multiple domains, select all these domains in the list of domains and click Limit Outgoing Messages.

    Alternatively, to edit a domain’s limit, click Limit Outgoing Messages on the pane under the domain name in Websites & Domains.

  3. Edit the Limit on outgoing messages field.

Setting Custom Limits for Mailboxes

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

  1. Go to Domains, select the domain for which you want to change the limit, and open its hosting settings in the Customer Panel.

  2. Go to the Mail > Email Addresses tab and click the email address for which you want to change the limit in the list of mailboxes.

    To set the same limit for multiple mailboxes, select all these mailboxes in the list of mailboxes and click Limit Outgoing Messages.

  3. Edit the Limit on outgoing messages field.

Note: Alternatively, you can use links from the Tools & Settings > Outgoing Mail Control in order to change custom limits for Plesk objects.