Courier and DCC

Earl Killian
Wed Apr 10 03:28:41 UTC 2002

Vernon Schryver writes:
 > Date: Tue, 9 Apr 2002 19:15:21 -0600 (MDT)
 > From: Vernon Schryver <>
 > >   The filters are executed during the smtp-conversation, and can
 > >   only accept or reject a message, not change it (so no headers).
 > The lack of headers would hurt dccproc whitelisting.

I think Vincent Schonau meant by "(so no headers)" that you wouldn't
be able to add the X-DCC* lines to the message header.

There are actually two phases to filtering: rcptfilters are called
after you have the HELO/MAIL FROM/RCPT TO, and you can give "thumbs
up", "thumbs down", or "maybe" at this point.  If you say "maybe",
then a second filtering phase is run after you have the SMTP DATA, but
before you give the DATA response.  This filter has access to the
message headers and body.

 > What else can be used for whitelisting (besides the envelope
 > Mail_from value)?  (I've found the envelope HELO value handy for
 > blacklisting).

The following environment variables are available to the filters:

SENDER		return address
TCPLOCALIP	IP address of this end of the connection
TCPLOCALPORT	port number of this end of the connection
TCPREMOTEIP	IP address of other end of the connection
TCPREMOTEPORT	port number of other end of the connection
TCPREMOTEINFO	Identification string received from the IDENT server
		on the remote IP address.

The one thing I didn't see was the HELO value!


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