sendmail, deferred: host name lookup fail

[Eliot Stock]

Hello.

I installed FC3 today and can receive mail just fine. Outgoing mail, 
however, is being queued by sendmail due to host name lookup failures. I 
send mail using my ISPs SMTP server as a smart host.

mailq shows every message in the queue with this error:

Deferred: Name server: relay.plus.net: host name lookup fail

I can dig relay.plus.net and it resolves just fine and I can ping it. I 
can't get an MX record for it however.

This worked fine on FC2, but I can't be completely sure my sendmail and 
name resolver config is exactly the same as I had on FC2.

Any clues anyone?

Cheers,

Eliot Stock.