[Mimedefang] filter_recipient questions

[Dirk the Daring]

   I've noticed a lot of dictionary spamming of late, and I was thinking
of enhancing my filter_recipient to help stop it. Right now, I basically
use filter_recipient to look for a HELO claiming to be me, or for an
E-Mail headed to my "whitelist request" address.

   What I'd like to add is something to check validity of local
recipients (using a mechanism other than md_check_against_smtp_server
for various political reasons that aren't important here), but I'm not
sure how the logic flow works.

   My questions are:

	1) Is filter_recipient called for each RCPT TO: (as would
		appear to be the case), or at DATA?

        2) The documentation states that if filter_recipient returns
		DISCARD, the message is discarded for ALL Recipients. Is
		this also true of REJECT (as would also appear to be
		the case)?

	3) Since it looks like filter_recipient can't be used to
		selectively (on a per-Recipient basis, allowing to some
		but not all) reject/discard a connection, can I have it
		alter a given Recipient envelope address so I can look
		for that "flag" in filter_begin and remove the
		Recipient there?

   My idea is something like (where "recipient_valid" is a function
I've written to check address validity, returning FALSE for a *valid*
address and TRUE for an *invalid* one):

	[....existing filter_recipient code...]
	if ( recipient_invalid($recipient) )
		{
		$recipient = "invalid\@domain.tld";
		return ('CONTINUE', "OK");
		}
	[...existing filter_recipient code....]

   and then

	[....existing filter_begin code...]

	[start loop to step thru @Recipients; $check is index...]
	if ( $Recipients[$check] =~ "invalid" )
		{
		delete_recipient($Recipients[$repindex]);
		}
	[...end loop to step thru @Recipients]

	[...some code to check if there are any valid Recipients left...]
	if ( $no_valid )
		{
		return('REJECT', "Dictionary SPAM rejected");
		}

	[...existing filter_begin code....]

   Feedback? Sane? Insane?

Dirk