temp avoiding RBL block with client_checks OK?

one of the users is waiting for an email from server currently listed on
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chances are it might get fixed in 12 hours, or, maybe not

short of removing from my RBL checks, is there a way to
'bypass' this current predicament, and, allow mails from the IP/host?

can I simply put IP ? hostname ? both ? in /etc/postfix/client_checks ?

or is it /etc/postfix/sender_checks ? as so: OK OK