Hi "don't check these hosts" in SMTP is for IP address of the sender public IP, not for domain or email address ...
And please solve the problem at source, your sender should have a valid reverse, this is in the SMTP RFC ...
an "Reject invalid reverse DNS :" is not necessary at "SMTP check" because it is also in the SpamC rules and will provide bad points to the fine tuning of the message.
Regards