[Spamcop can not send me mail]

I tried configuring a mailhost today and it fails with:

450 4.7.25 Client host rejected: cannot find your hostname, [184.94.240.100]

Postfix when configured with reject_unknown_client_hostname is rejecting the mail because the sender has invalid DNS records:

Quote

reject_unknown_client_hostname (with Postfix < 2.3: reject_unknown_client)

Reject the request when 1) the client IP address->name mapping fails, or 2) the name->address mapping fails, or 3) the name->address mapping does not match the client IP address.
This is a stronger restriction than the reject_unknown_reverse_client_hostname feature, which triggers only under condition 1) above.
The unknown_client_reject_code parameter specifies the response code for rejected requests (default: 450). The reply is always 450 in case the address->name or name->address lookup failed due to a temporary problem.

Postfix logs:

Apr  6 11:44:26 mail postfix/postscreen[1602]: CONNECT from [184.94.240.100]:32832 to [xxxx]:25
Apr  6 11:44:26 mail postfix/postscreen[1602]: PASS OLD [184.94.240.100]:32832
Apr  6 11:44:27 mail postfix/smtpd[33315]: warning: hostname vmx.spamcop.net does not resolve to address 184.94.240.100
Apr  6 11:44:27 mail postfix/smtpd[33315]: connect from unknown[184.94.240.100]
Apr  6 11:44:28 mail postfix/smtpd[33315]: NOQUEUE: reject: RCPT from unknown[184.94.240.100]: 450 4.7.25 Client host rejected: cannot find your hostname, [184.94.240.100]; from=<service@admin.spamcop.net> to=<xxxx> proto=SMTP helo=<prod-sc-www02.spamcop.net>
Apr  6 11:44:28 mail postfix/smtpd[33315]: lost connection after RCPT from unknown[184.94.240.100]
Apr  6 11:44:28 mail postfix/smtpd[33315]: disconnect from unknown[184.94.240.100] helo=1 mail=1 rcpt=0/1 commands=2/3

Is it possible for the SC admins to correctly setup DNS or hostname so that the name is resolved properly?

Currently I get:

nslookup 184.94.240.100
100.240.94.184.in-addr.arpa     name = vmx.spamcop.net.

# dig vmx.spamcop.net mx
;; QUESTION SECTION:
;vmx.spamcop.net.               IN      MX

;; ANSWER SECTION:
NO ANSWER

;; AUTHORITY SECTION:
spamcop.net.            59      IN      SOA     ns1-93.akam.net. hostmaster.akamai.com. 2023032702 300 300 300 300

# dig vmx.spamcop.net a
;; QUESTION SECTION:
;vmx.spamcop.net.               IN      A

;; ANSWER SECTION:
vmx.spamcop.net.        69      IN      A       184.94.240.112

Thanks!