Recipient MTA is rejecting bounces

[Yusuf Goolamabbas]

Hi, I have a qmail-1.03 machine saw in my queue a few bounces in
them. Also, looking at my logs I saw the following message

@400000003905243f24daf1b4 delivery 34: deferral:
Connected_to_204.68.180.50_but_sender_was_rejected./Remote_host_said:_451_<#@[]>..._unresolvable_host_name_[],_see_RFC_1123,_sections_5.2.2_and_5.2.18./

Is the recipient MTA correct in its behaviour or have I misconfigured
something on my side

Regards, Yusuf

-- 
Yusuf Goolamabbas
[EMAIL PROTECTED]