Virtual spam forwarding issues

2 msg	2 postfix server on the same domain in differen...
3 msg	mailer-deamon sends error messages to: question
3 msg	Procmail
15 msg	MAIL FROM timeout with ciphers=high
2 msg	milter, broken pipe
17 msg	How to listen on 587 as well as 25?
6 msg	reject_sender_login_mismatch doesnt work
2 msg	smtp auth
4 msg	Postfix with MYSQL compile error
8 msg	mynetworks=<empty> vs mynetworks=<defa...
3 msg	message_size_limit with ldap search parameter
2 msg	Pipe debugging
12 msg	destination_concurrency_limit not respected ?

Virtual spam forwarding issues
\ Michael McDermott (29 Nov 2007)
. \ Terry Carmen (29 Nov 2007)
. . \ mouss (29 Nov 2007)
. . . \ Jorey Bump (29 Nov 2007)
. . . . \ Terry Carmen (29 Nov 2007)
. . . . . \ Michael McDermott (29 Nov 2007)
. . . . . \ Jorey Bump (29 Nov 2007)
. . . . . . \ Gerard (30 Nov 2007)
. . . . . . . \ Jorey Bump (30 Nov 2007)
. . . . . . . . \ Michael McDermott (30 Nov 2007)
. . . . . . . . . \ Jorey Bump (30 Nov 2007)
. . . . . . . . . . \ Michael McDermott (30 Nov 2007)
. . . . \ mouss (29 Nov 2007)

2 msg	cleaning up deferred queue
2 msg	static nexthop per domain
2 msg	Simple postmap question
9 msg	Issues with Recipient_Canonical mapping
3 msg	Mail server reboot after got flood
3 msg	can't create a virtual domain

Subject:	Virtual spam forwarding issues
Group:	Postfix-users
From:	Michael McDermott
Date:	29 Nov 2007

I am using Postfix 2.3.8 with virtual mail accounts. Each mail account has a
.Spam maildir. In current delivery spam and non-spam come into postfix,
which is then forwarded if there is a virtual_alias_maps entry and passed
onto maildrop if there is no virtual_alias_maps entry. Maildrop calls
SpamAssassin and filters spam into the .Spam maildir and normal mail into
the normal maildir. (Pretty standard setup).

However, I want to be able to filter spam before Postfix ever has the
opportunity to forward it. The reason for doing this is to avoid problems
I'm having with some ISPs because I'm forwarding spam onto their accounts
without filtering it. In order to do this I have set up spampd to call
SpamAssassin, which then passes the email back to Postfix. Postfix then runs
a header_checks to see if SpamAssassin filtered the mail as spam. After that
I am at a loss. It seems that there is no way to prevent Postfix from
forwarding the spam on to the forwarding address.

I tried passing the spam to the virtual delivery agent via a FILTER command.
However, the virtual delivery agent cannot do anything other than deliver
the spam email to the local maildir or bounce it back (bounce then takes the
bounceback spam, sends it to the original sender which is then forwarded
onto the recipient, which is rather humorous). The spam email is ultimately
forwarded, so this does not work.

I tried passing the spam to the local delivery agent via a FILTER command,
and then using luser_relay to pass the email onto a local account. I setup a
spamluser user on my box and it seems to work fine. Problem is that all spam
is passed to the spamluser and never reaches the user maildir in the case of
non-forwarded email. I could use .forward or procmail to send the spam back
to the user but that creates a forwarding loop. The local .forward or
procmail cannot deliver to the user maildir.

I investigated perhaps sending the spam to another smtpd agent, but this
seems to create more forwarding loop problems.

Basically I have to somehow rewrite the spam email in real-time so that it
is not forwarded after it has been filtered. I was wondering if this is
possible, and if it is not then what Postfix users would recommend for
solving this problem.