Last modified: September 22, 2021

Overview

The Mail section of WHM’s Tweak Settings interface (WHM » Home » Server Configuration » Tweak Settings) contains five options that allow you to limit outgoing mail. The limits that these options set apply to all domains on the server. Use the options to help limit bandwidth consumption and prevent potential spammers.

Total emails sent by a domain per hour options

The following options apply to the total number of outgoing messages that a domain sends per hour.

Max hourly emails per domain

The Max hourly emails per domain option limits the number of messages that a domain can send per hour.

Attributes

• cpanel.config entry: maxemailsperhour

• Default value: Unlimited (no value)

• Minimum value: 1

• Maximum value: Unlimited (no value)

• Permissions: — A user with either of the following permissions can access this option:

  • A reseller account, if you enable the Allow Creation of Packages with non-default Email Limits option in WHM’s Edit Reseller Nameservers and Privileges interface (WHM » Home » Resellers » Edit Reseller Nameservers and Privileges)
  • A user with root-level privileges.

Count mailman deliveries towards a domain’s Max hourly emails

This setting allows you to specify whether to count messages sent to Mailman mailing lists against an account’s Max hourly emails per domain limit.

• Set this option’s value to On to include Mailman deliveries in the total value that a domain’s Max hourly emails per domain option uses.

• Set this option’s value to Off to exclude Mailman deliveries from the total value.

Attributes

• cpanel.config entry: email_send_limits_count_mailman

• Default value: Off

• Permissions: A user with root-level permissions can access this option.

The percentage of email messages (above the account’s hourly maximum) to queue and retry for delivery

This option defines how the mail server handles outgoing messages for a domain that reaches the value of the Max hourly emails per domain option. The mail server will attempt to deliver any queued messages in the next hour, by default.

• To discard all additional outgoing messages for a domain after the domain reaches the value of the Max hourly emails per domain option, enter 100 in the The percentage of email messages (above the account’s hourly maximum) to queue and retry for delivery text box.

• To queue outgoing messages for a domain after the domain reaches the value of the Max hourly emails per domain option, enter a value larger than 100 in the The percentage of email messages (above the account’s hourly maximum) to queue and retry for delivery text box.

Attributes

• cpanel.config entry: email_send_limits_defer_cutoff

• Default value: 125

• Minimum value: 100

• Maximum value: 10000

• Permissions: A user with root-level permissions can access this option.

Example

You set the Max hourly emails per domain option to 100, and you set the The percentage of email messages (above the account’s hourly maximum) to queue and retry for delivery option to 200. The mail server applies the following rules to the outgoing messages from each domain:

• The mail server sends the first 100 outgoing messages from the domain.

• The mail server queues the next 100 outgoing messages from the domain.

• The mail server discards any additional outgoing messages from the domain.

• In the following hour, the mail server attempts to send all queued outgoing messages from the domain.

Total emails sent by an email account per hour options

The following options apply to the total number of outgoing messages that an individual email account sends per hour.

Number of unique recipients per hour to trigger potential spammer notification.

The Number of unique recipients per hour to trigger potential spammer notification. setting specifies the number of emails that any account may send in one hour before the system sends an alert notification.

If an email account exceeds this threshold and the system administrator has enabled the Large Amount of Outbound Email Detected alert in WHM’s Contact Manager interface (WHM » Home » Server Contacts » Contact Manager), the system will send an alert to the system administrator.

Failed and deferred outgoing message options

The Maximum percentage of failed or deferred messages a domain may send per hour option and the Number of failed or deferred messages a domain may send before protections can be triggered option specifies when the server will temporarily block outgoing mail from a domain. The system examines all outgoing and local mail over the previous hour to determine whether these conditions are true.

Example

Number of failed or deferred messages a domain may send before protections can be triggered

This option defines how many failed or deferred messages that a domain can send before the mail server checks whether the Maximum percentage of failed or deferred messages a domain may send per hour value was met.

Attributes

• cpanel.config entry: email_send_limits_min_defer_fail_to_trigger_protection

• Default value: 5

• Minimum value: 1

• Maximum value: 1000000000000000000

• Permissions: A user with root permissions can access this option.

Maximum percentage of failed or deferred messages a domain may send per hour

This option specifies the maximum percentage of failed or deferred messages that a domain may send per hour. This option only applies after the number of failed or deferred messages reaches the Number of failed or deferred messages a domain may send before protections can be triggered option’s value.

Attributes

• cpanel.config entry: email_send_limits_max_defer_fail_percentage

• Default value: Unlimited

• Minimum value: 1

• Maximum value: Unlimited

• Permissions: A user with root permissions can access this option.

Error message

If a domain reaches the limits set in the Maximum percentage of failed or deferred messages a domain may send per hour and Number of failed or deferred messages a domain may send before protections can be triggered options set, then your error log will contain entries that resemble the following example:

R=enforce_mail_permissions: Domain example.com has exceeded the max defers and failures per hour (7/5 (20%)) allowed. Message discarded.

The number of failed and deferred outgoing messages affect the values in the error message in the following ways:

• 7 — The number of failed or deferred outgoing messages from the domain in the hour.

• 5 — The number of failed or deferred messages the mail server allows the domain to send in an hour, before it checks the percentage of failed or deferred outgoing messages that the mail server allows the domain to send. To set this value, use the Number of failed or deferred messages a domain may send before protections can be triggered option.

• 20 — The current percentage of deferred or failed outgoing messages for the domain. This percentage is based on the total messages sent compared to the number of failed or deferred outgoing messages per hour for the domain.