max_outbound_connections

March 26, 2020 Contributors

Name

max_outbound_connections — set the maximum number of outbound connections for a domain

Synopsis

Max_Outbound_Connections = 32

Description

This will limit the number of outbound connections to an individual domain to the specified value. It can be set at a global level, which enforces the limit on every domain in the system, or at a binding, binding_group or domain level. When this option is set in the domain, binding or binding_group scope the global value is overridden and the usual fallback semantics apply. The default value for this option is 32. Note: When used in the Host scope, Max_Outbound_Connections limits the number of connections to the specified IP address.

Usage Example

Find below an example of how this configuration option might be used:

Max_Outbound_Connections = 30

Domain "example.com" {
  dkim = "enabled"
}

Binding_Group "group1" {

  Max_Outbound_Connections = 5

  Binding "example" {

    Bind_Address = "10.10.10.10"
    Max_Outbound_Connections = 15

    Domain "example.com" {
      #some other options
      ...
    }
  }

}

When connecting to example.com from the example binding, Max_Outbound_Connections will be 15, when connecting from another binding in the group1 group it will be 5 and when connecting from a binding that is not in the group1 group it will be 30.

In some circumstances it may make sense to declare a domain within a binding and also declare it globally—when you want interaction with that domain to be different globally versus in a particular binding. For example, with the following configuration customers on the yahoofriends binding are allowed to use 30 connections to yahoo.com, customers on other bindings are allowed to use only 10 connections per binding to yahoo.com, and connections to domains other than yahoo.com are unrestricted.

Binding "yahoofriends" {
  Domain "yahoo.com" {
    Max_Outbound_Connections = 30
  }
}

Domain "yahoo.com" {
  Max_Outbound_Connections = 10
}

Max_Outbound_Connections in the host Scope

Note that the usual semantics do not apply with this option in the host scope. If you declare a host scope and do not define Max_Outbound_Connections, its value will be -1 and not the fallback value of Max_Outbound_Connections in an encompassing scope.

Given the following configuration file:

Max_Outbound_Connections = 32
host "example.com" {}

You will see the following results from the system console:

09:45:58 /tmp/2025> config eval max_outbound_connections
Max_Outbound_Connections = 32
09:46:29 /tmp/2025> config eval host example.com max_outbound_connections
Max_Outbound_Connections = -1

A setting of -1 means that unlimited connections are allowed.

Scope

max_outbound_connections is valid in the binding, binding_group, domain, global and host scopes.

See Also

host, “MultiVIP© Interfaces”, server_max_outbound_connections, “Configuration Scopes and Fallback”, scope_max_outbound_connections