delineating DRIP

On Wed, Oct 08, 2003 at 01:03:13PM -0400, Alan DeKok wrote:
| 
|   The use of DNS-based filtering on EHLO/HELO has many fewer problems
| and issues than that for MAIL FROM.
| 

>From the point of view of an ISP, designated sender schemes are good for
three reasons:

 1) because we can perform DS checks, we get fewer spams coming in.
 2) specifically, because the checks occur before DATA, we save bandwidth and CPU.
 3) because SPF/RMX/DMP protect mail-from, we get fewer spam/virus bounces.

My understanding of DRIP is that it does not share #3.

Is that correct?

It seems to me that DRIP is most similar to PTR checks --- if the
sending host has no PTR records, it's not "designated".  It is more
flexible because vanity domains on broadband nodes can create records
for DRIP, but not for PTR.

In a DRIP world, ISPs are likely to suffer a higher spam/virus bounce
rate than in an RMX/SPF/DMP world.  Is that correct?