Courier and DCC

Vincent Schonau
Wed Apr 10 17:16:58 UTC 2002

On Tue, Apr 09, 2002 at 09:34:49PM -0600, Vernon Schryver wrote:
>> From: "Earl Killian" <>
>> 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.
> How do they handle multiple RCPT_TO values?

When a recipients mailfilters reject the message, an appropriate 5xx
response is issued during the SMTP conversation. If some recipients want
to accept, but others don't, and the sending SMTP client continues after
this 5xx error (with DATA), the mail will be delivered to the address
who had accepted the message, but not to those that hadn't.

This seems appropriate; it works with my installations. I'm not quite
sure how mailservers other than qmail respond to seeing 5xx during the
SMTP-conversation, especially before DATA.

There's a blurb in the localmailfilter documentation that refers to
'users being unsubscribed from mailing lists due to other users poorly
written filters'. 

>> ...
>> TCPREMOTEINFO	Identification string received from the IDENT server
>> 		on the remote IP address.
>> The one thing I didn't see was the HELO value!

The HELO value is reproduced as

 Received: from <helo-value>

in the top Received: header, available to smtpfilter.

> TCPREMOTEINFO is also odd, since the IDENT value is of very
> limited use and a major hazard for slowing down a busy system.

The tcp-daemon used (couriertcpd) can be configured not to obtain IDENT
info. If it's configured to get it, it passes it on to the smtp-server.


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