[Top] [All Lists]

Re: limiting SPAM

2003-11-22 09:27:11
On Sat, 22 Nov 2003 10:31:54 EST, "Richard O. Hammer" 
<ROHammer(_at_)EarthLink(_dot_)net>  said:
Is there something which prevents spammers from sending their messages 
with a null reverse path in the envelope?  In other words, with
in the SMTP exchange?

You do that, and I'll be forced to block mail from your site, and toss your
domain at the nice guys at  I have better
things to do than accept mail from sites that won't accept bounce messages
back. You send the mail, it bounces, the bounce goes back with a MAIL FROM:<>
as per the RFC, and if you don't accept the bounce, then:

a) your user never learns they sent to the wrong address and it bounced.

b) the double bounce ends up in *my* inbox and I get irate.

Unfortunately, any reasonable counter measures here require you to let
things go past the DATA step:

1) Check the body of the mail to see if it's either an RFC3491/3492 style
DSN or any of the more common non-RFC format bounces (AOL, qmail, and MS 
are some of the biggies here).

2) If it isn't a bounce message but has MAIL FROM:<>, toss it.  Note that
this *WILL* false-positive on some things (most notably, LSoft's Listserv
product sends confirmation requests for subscriptions with <>, specifically
so if the remote address is bad, it doesn't get a bounce message it doesn't
care about).

3) Note that I've *also* already seen spammers sending their spam inside
properly formatted bounces, specifically to work around the loophole you're
trying to create.

Attachment: pgpzi2uSz9wo5.pgp
Description: PGP signature

<Prev in Thread] Current Thread [Next in Thread>