Domain of sender address does not resolve

["Ravi Prakash B.V." <ravibv@xxxxxxxxxxxxxxxx>]

Hi,
I configured mail server for our network using sendmail. It is working
finely.
But I am unable to send mails to some mailservers like joymail,
india.sun.com,eci.ericsson.se etc.

For example:
Jan 25 11:30:07 atcmail sendmail[14475]: LAA14474:
to=<hrhyd.ecir@xxxxxxxxxxxxxxx>, ctladdr=<sumalatha@xxxxxxxxxxxxx>
(508/508), delay=00:03:18, xdelay=00:03:06, mailer=esmtp,
relay=alaska-ext.wise.edt.ericsson.se. [194.237.142.111], stat=Deferred:
451 4.1.8 <hrhyd.ecir@xxxxxxxxxxxxxxx>... Domain of sender address
sumalatha@xxxxxxxxxxxxx does not resolve

I checked in sendmail faqs, sendmail mailing lists also.... From the
mailing list, I came to know that it is failing when the destination is
trying to identify the sender domain (through reverse DNS)...
I checked with our DNS and as well as destination DNS to resolve our
domain name, it is working finely.
I am unable to identify the problem..
give some pointers or any clue to solve this problem...

Thanks in advance,
Ravi Prakash