DNS/Email transfer problem; sender's domain doesn't exist??

[Madison Kelly]

Hi all,

   I've noticed that occasionally mail sent from 'nouvelocity.com' gets 
bounced back with the following error. When I saw this in the past it 
was because of DNS issues but as best as I can see everything is 
working. Anyone run across this before? Thanks!!

Madison

  =- Error (names changed to protect the innocent) -=
This is the Postfix program at host domain.com.

I'm sorry to have to inform you that the message returned
below could not be delivered to one or more destinations.

For further assistance, please send mail to <postmaster>

If you do so, please include this problem report. You can
delete your own text from the message returned below.

The Postfix program

<info-Z/ri2g1+kVzocAvg7RY1XgC/G2K4zDHf at public.gmane.org>: host mail.anotherdomain.com[111.222.210.68]

said:

     553 5.1.8 <info-39QC8RyHzSPYv3AteYhma1aTQe2KTcn/@public.gmane.org>... Domain of sender address
     user-UqHW2wehKNmfJOJzLBvvIA at public.gmane.org does not exist (in reply to RCPT TO command)

<user.name-H217xnMUJC0sA/PxXw9srA at public.gmane.org>: host smtp2.ns.utoronto.ca[128.100.132.58] said:

553

   5.1.8 <user-UqHW2wehKNmfJOJzLBvvIA at public.gmane.org>... Domain of sender address
   user-UqHW2wehKNmfJOJzLBvvIA at public.gmane.org does not exist (in reply to MAIL FROM command)

  <user.name-ymHb0DOz3BmnS0EtXVNi6w at public.gmane.org>: host smtpgw1.gov.on.ca[192.75.156.245]

said:

      501 5.1.8 Sender domain must exist (in reply to MAIL FROM command)

<user.name-/Aqni/cABlKnS0EtXVNi6w at public.gmane.org>: host govonca2.gov.on.ca[192.75.156.245]

said:

      501 5.1.8 Sender domain must exist (in reply to MAIL FROM command)
  =- End Error -=
--
The Toronto Linux Users Group.      Meetings: http://tlug.ss.org
TLUG requests: Linux topics, No HTML, wrap text below 80 columns
How to UNSUBSCRIBE: http://tlug.ss.org/subscribe.shtml