Outbound Requests

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Send outbound DNS and zone transfer requests via
Specify which IP versions (IPv4/IPv6) and from which local IP addresses outbound requests should be sent.
It can be useful to select a specific local IP address for secondary DNS servers with multiple IP addresses (multi-homed) if the primary DNS server only allows zone transfers from a specific IP address.
When both IPv4 and IPv6 are enabled, you can also enabled "Prefer IPv6 servers" to have the server attempt to resolve DNS over IPv6 whenever possible.

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Send outbound DNS requests from port number
Specify if Simple DNS Plus should use a system assigned port number or a specific port number to send outbound requests from.
Using system assigned port number is recommended, but in some cases it may be necessary to use a specific port number to pass through strict firewalls policies.