i have two testing sendmail servers named ashu.yahoo.com and tinu.google.com both are slave of each others too
they have entry for each others like in yahoo.com
IN NS ashu.yahoo.com.
IN NS tinu.goolge.com.

and same thing for reverse zone too both can see each others PTR records like from yahoo.com
i can use host command on google.com both via hostname and ip as well this works on either side

i have an very basic sendmail setup
the "PROBLEM" is user can send mail within the domain but not across domain like user1 at ashu.yahoo.com can sendmail to user2@ashu.yahoo.com but not to user2@tinu.google.com
same thing with google.com both cant send mails to each others
users get error pls see the attached pix

Please help me