outbound-msg-retry definition query

[ashok athukuri via Unbound-users]

Hello All,

As per https://nlnetlabs.nl/documentation/unbound/unbound.conf/

outbound-msg-retry: *<number>*
            The number of retries Unbound will do in case of  a  non  positive
            response is received. If a forward nameserver is used, this is the
            number of retries per forward nameserver in case of throwaway  re-
            sponse.

*what is "non positive" response here SERVFAIL or NXDOMAIN or BOTH?*

Thanks,
Ashok