reject_unknown_client_hostname when nameserver is unreachable

[Karel]

Hello,

I am using following smtpd_client_restriction:

  reject_unknown_client_hostname

Now, both my nameservers were offline, and postfix could not resolve IP
addresses and thus rejected all hosts:

  NOQUEUE: reject: RCPT from unknown[x.x.x.x]: 450 4.7.1 Client host
rejected: cannot find your hostname, [x.x.x.x]

I know that unreachable nameservers are a problem of its own, and that
it should not happen. But still, is there anything I can do in Postfix
to mitigate this, should it happen again?

thanks,
Karel