The network configuration adapters is entered directly into the underlying Windows Network Settings and it uses standard Windows behavior with regards to DNS servers and lookups.
Safeguard sends the name query to the 1st DNS server on X0 adapter's list and waits 1 second for a response. If Safeguard does not receive a response from the 1st DNS server within this time, it will then send the name query to all DNS servers on the preferred adapter's list and wait 2 seconds and so on... until (8 seconds) in which case if Safeguard has not received a response from any server, it will respond with a timeout.
The Safeguards DNS client service internally will keep track of which servers answer the name query quickly and it will move the servers up or down on the list based on how quickly they reply to name queries.
The DNS query will stop when a response has been received, regardless of whether it was successful or negative response. This means it is not possible to forward the request to a second DNS server if the first has given a negative response.