sendmail - reverse lookup problems

[Boex,Matthew W.]

another odd problem with reverse lookup's.  we are able to send mail to
na.bestfoods.com [12.14.84.10].  They cannot send mail to us.  They can do
an nslookup and get our mx record.  Sendmail, on our end, I think is timing
out trying to reverse lookup their outbound mail server.  They tell me the
server is 12.14.84.35.   when i do an nslookup 12.14.84.35 i get nothing.
when i do a dig -x 12.14.84.35 it reports that att.net is authoritative for
their domain, and the PTR record is aliased?  i think.  

why is nslookup showing nothing
why is sendmail choking on an aliased PTR record?  Should it be choking?  

matt