Question : Relaying denied. IP name lookup failed

I'm getting the below error and I've been on the phone with Red Hat for over 2 hours and they cannot figure it out. It seems like a simple question, wWhy is relaying being denied? Here's the entry in the /var/log/maillog

Nov 30 08:58:35 mammoth sendmail[13583]: lAUGwYMT013583: ruleset=check_rcpt, arg1=, relay=[66.51.204.153], reject=550 5.7.1 ... Relaying denied. IP name lookup failed [66.51.204.153]

The domain name is geoffandcindy.com and it has a valid MX record.  The local-host-names has the domain in it 'geoffandcindy.com' and sendmail.mc has the following special options enabled along with the normal other ones:
define(`confAUTH_OPTIONS', `A p y')dnl
TRUST_AUTH_MECH(`LOGIN PLAIN')dnl
define(`confAUTH_MECHANISMS', `LOGIN PLAIN')dnl
define(`confTO_IDENT', `0')dnl
FEATURE(delay_checks)dnl
FEATURE(`no_default_msa',`dnl')dnl
FEATURE(`smrsh',`/usr/sbin/smrsh')dnl
FEATURE(`mailertable',`hash -o /etc/mail/mailertable.db')dnl
FEATURE(`virtusertable',`hash -o /etc/mail/virtusertable.db')dnl
FEATURE(redirect)dnl
FEATURE(always_add_domain)dnl
FEATURE(use_cw_file)dnl
FEATURE(use_ct_file)dnl

Answer : Relaying denied. IP name lookup failed

Try

define(`confAUTH_OPTIONS', `A y')dnl

or

define(`confAUTH_OPTIONS', `A')dnl