problems sending email to Barracuda protected sites

[stfaprc]

This is what Barracuda claims:
[highlight][tt]The null sender server, "server.us.org", should have their server records/mail configuration corrected to provide a valid return path.[/tt][/highlight]

OK, what are they talking about? What should I be looking for?
Is this a sendmail or DNS thing? Both?

thanks,

 

[elgrandeperro]

Does your email have a return MX record? That is what it is asking...

 

[stfaprc]

when I go to a different network and try
dig us.org MX
it returns
;; ANSWER SECTION:
us.org. 1W IN MX 15 server.us.org.

dig server.us.org MX
does not return an ANSWER SECTION

Do they want me to put in the named.conf
server.us.org. IN MX 10 server.us.org.

or is there a change to sendmail to be made?

 

[elgrandeperro]

I believe they want a return MX for server.us.org., as you have there.