Zhang,
I have removed the previous entries from the header_checks file and configured the smtpd_recipient_restrictions, as you said. The connections are still coming in the /var/log/mail.log. Please see below. But I think now we are atleast rejecting these connection requests efficiently at the mailserver in addition to the EmailID deletion.
Thanks.
Apr 25 16:09:37 mydomain postfix/smtpd[15165]: connect from 216-80-120-215.prs-bsr1.chi-prs.il.static.cable.rcn.com[216.80.120.215]
Apr 25 16:09:38 mydomain postfix/smtpd[15165]: NOQUEUE: reject: RCPT from 216-80-120-215.prs-bsr1.chi-prs.il.static.cable.rcn.com[216.80.120.215]: 554 5.7.1 <job@mydomain.org>: Recipient address rejected: Detected as Spam; from=<New-Zealand-Jobs.032M@NEWJOBSABROAD.COM> to=<job@mydomain.org> proto=SMTP helo=<NEWJOBSABROAD.COM>
Apr 25 16:09:38 mydomain postfix/smtpd[15165]: disconnect from 216-80-120-215.prs-bsr1.chi-prs.il.static.cable.rcn.com[216.80.120.215]