mail forwarding loop: how do I prevent this?

5 msg	postconf not displaying all options
3 msg	empty_address_recipient not mapped by virtual o...
5 msg	stop smtp from anyone unless sasl auth?
2 msg	'piped' aliases & DSNs
12 msg	Strange From: in headers
5 msg	Mail - Access Denied
4 msg	qpsmtpd support service for postfix
39 msg	pix workaround broken?
2 msg	X-Original-To after bcc contains wrong address
8 msg	/usr/lib/sendmail delivery status/message id's ...
23 msg	Recommended Filesystems?
8 msg	Mail going to backup server instead main server
3 msg	outgoing rate control

mail forwarding loop: how do I prevent this?
\ Justin Piszcz (21 Jul 2007)
. \ (Wietse Venema) (21 Jul 2007)
. . \ Justin Piszcz (21 Jul 2007)
. . . \ mouss (21 Jul 2007)
. \ Bill Weiss (21 Jul 2007)

5 msg	Server relaying existing virtual mailbox
1 msg	how can I rewrite the Mail From
3 msg	Constant connections from user unknown sending ...
2 msg	sporadic deferrals
8 msg	transport_maps: different behavior if discard o...
4 msg	Address verification questions

Subject:	mail forwarding loop: how do I prevent this?
Group:	Postfix-users
From:	Justin Piszcz
Date:	21 Jul 2007

I did not have debug enabled when this happened, but how can someone cause
this who is not whitelisted? They appear to have made the mail server
send a bounce back to them?

Jul 21 07:20:48 l2 postfix/smtpd[4064]: 96AF0C08489B:
client=ns1.inamai.lt[87.239.113.1]
Jul 21 07:20:49 l2 postfix/cleanup[4077]: 96AF0C08489B:
message-id=<50c201c7cb97$51e04160$ea29bed5>
Jul 21 07:20:49 l2 postfix/qmgr[9471]: 96AF0C08489B:
from=<rimai>, size=3283, nrcpt=1 (queue active)
Jul 21 07:20:49 l2 postfix/local[4079]: 96AF0C08489B:
to=<ap>, relay=local, delay=12, delays=12/0.01/0/0.04,
dsn=5.4.6, status=bounced (mail forwarding loop for ap)
Jul 21 07:20:49 l2 postfix/cleanup[4077]: 3E031C08974C:
message-id=<20070721112049.3E031C08974C>
Jul 21 07:20:49 l2 postfix/qmgr[9471]: 3E031C08974C: from=<>, size=5026,
nrcpt=1 (queue active)
Jul 21 07:20:49 l2 postfix/bounce[4081]: 96AF0C08489B: sender non-delivery
notification: 3E031C08974C
Jul 21 07:20:49 l2 postfix/qmgr[9471]: 96AF0C08489B: removed
Jul 21 07:20:52 l2 postfix/smtpd[4064]: disconnect from
ns1.inamai.lt[87.239.113.1]
Jul 21 07:20:56 l2 postfix/smtp[4083]: 3E031C08974C: to=<rimai>,
relay=mail.inamai.lt[87.239.112.1]:25, delay=7.1,
delays=0.02/0.01/6.5/0.64, dsn=2.0.0, status=sent (250 2.0.0
l6LBOKBv065117 Message accepted for delivery)
Jul 21 07:20:56 l2 postfix/qmgr[9471]: 3E031C08974C: removed