[svlug] Email mystery...

[Michael Robinson]

Where are the email headers of the following backed up messages?
I'm using mbox format mailboxes and the standard /var/spool/postfix.

[root at goose64 /]# mailq
-Queue ID- --Size-- ----Arrival Time---- -Sender/Recipient-------
E607560191    16014 Fri Dec 26 12:14:01  MAILER-DAEMON
(Host or domain name not found. Name service error for name=cvpac.com
type=MX: Host not found, try again)

seniorliving-deemcr=robinson-west.com at cvpac.com

12B4E5FDCE    17332 Tue Dec 23 08:10:57  MAILER-DAEMON
(Host or domain name not found. Name service error for
name=bettyphan.com type=MX: Host not found, try again)

sandals-deemcr=robinson-west.com at bettyphan.com

1324860184    15758 Fri Dec 26 09:53:56  MAILER-DAEMON
(Host or domain name not found. Name service error for
name=saglikindex.com type=MX: Host not found, try again)

cableservice-deemcr=robinson-west.com at saglikindex.com

945745FDCB    18262 Tue Dec 23 06:05:51  MAILER-DAEMON
(Host or domain name not found. Name service error for
name=attorneydb.com type=MX: Host not found, try again)

smallbusinessloan-deemcr=robinson-west.com at attorneydb.com

-- 66 Kbytes in 4 Requests.
[root at goose64 /]# 

I'm wondering if my server is just trying to bounce messages or if
some host on my lan is trying to spam innocent people.  Is there a
simple way to tell postfix, don't bounce to nonexistent email 
exchangers?