SPAMHAUS BLOCKLIST ADDRESS IS WRONG MUST FIX Error and Solution

I've configured RBL for my postfix based mail server and I'm getting an error that read as follows:

May 3 04:35:37 mx02 postfix/smtpd[10956]: NOQUEUE: reject: RCPT from ant251.neoplus.adsl.tpnet.pl[83.26.101.251]: 554 5.7.1 Service unavailable; Client host [83.26.101.251] blocked using xen.spamhaus.org; SPAMHAUS BLOCKLIST ADDRESS IS WRONG MUST FIX; from= to= proto=ESMTP helo=

How do I fix this problem?

This error clearly indicate that you are using wrong rbl dns address name xen.spamhaus.org. The correct address is zen.spamhaus.org. Thus you must use something as follows in postfix:

smtpd_recipient_restrictions =
  permit_mynetworks,
  permit_sasl_authenticated,
  reject_non_fqdn_hostname,
  reject_non_fqdn_sender,
  reject_non_fqdn_recipient,
  reject_unauth_destination,
  reject_unauth_pipelining,
  reject_invalid_hostname,
  reject_rbl_client zen.spamhaus.org

Save and close the file and restart the postfix:
# service postfix restart
OR
# service postfix reload
You can always verify queries using host / dig tool from a shell prompt:
$ host -t a 208.43.79.236.zen.spamhaus.org
Output:

Host 208.43.79.236.zen.spamhaus.org not found: 3(NXDOMAIN)

$ host -t a 208.43.79.236.xen.spamhaus.org
Output (note xen.spamhaus.org is an incorrect Spamhaus server address, so you will get an error):

208.43.79.236.xen.spamhaus.org is an alias for blocklist.address.is.wrong.spamhaus.org.
blocklist.address.is.wrong.spamhaus.org has address 127.0.0.2