Question : Message not transferred to xxx 450.4.7.1 Client host rejected

We are running Domino 8.5 for email and are getting errors when sending to certain clients.
Message not transferred to xxx 450.4.7.1 Client host rejected: cannot find your hostname, [193.132.29.230]

Other messages also include

451 Blocked - Reverse DNS queries for your IP fail
421 Refused - Your reverse DNS entry ddoes not resolve.

As far as I can tell our reverse DNS is resolving when I use the tool from www.dnstrouble.com

Our external IP is 193.132.29.230

Answer : Message not transferred to xxx 450.4.7.1 Client host rejected

Your reverse DNS for that IP resolves to ukmail01.moog.com. Check if that matches the sending email address you are using. If that is correct i would contact the recepient mailserver admin, could be a DNS problem on their side.