rDNS problem ?

[Bill.Light at kp.org]

I host an apache server with multiple low-volume family web-sites for mail 
and family pictures, etc.
I thought I had everything squared away for the last year or so, but my 
youngest is trying to reply to craigslist here in the San Francisco area 
and gets a returned mail message:

                        The Postfix program

<comm-380120213 at craigslist.org>: host mxi4s.craigslist.org[66.150.243.11] 
said:
    554 <unknown[66.124.156.123]>: Client host rejected: rDNS/DNS 
validation
    failed. Please setup matching DNS and rDNS records:
    http://bind8nt.meiway.com/itsaDNSmess.cfm (in reply to RCPT TO 
command)

Is it really DNS or do I go looking at my postfix configuration? 
version.bind    text = "9.2.4"

He is sending from username at hall-brothers.com, and mail should be handled 
by mail.light-family.com

Where do I go looking?