Author: Ted Cooper Date: To: exim-users Subject: Re: [exim] Fwd: blocking annoying 'bounce mail' "feature"
fromcustomers use.
On 31/05/11 02:22, Todd Lyons wrote: > This is from the NANOG list. Is anybody else attempting to prevent
> backscatter by blocking emails from customers using smtp auth that the
> sender is <> or postmaster (and recipient is not local)? This is not
> something I have ever considered, looking to see if anybody else has.
Not quite along the same vein, but close .. it's on a gateway for a
business network.
I have one customer who used to get themselves blocked constantly with
backscatter. They would complain to me, I would explain why they needed
to change what they do, they would say they couldn't do it because of
X,Y and Z. So I did it for them and they haven't noticed yet.
They would send out MSexchange vaction replies to any external address
that sent to them any time the person left the office, including outside
work hours.
I do not have control over this exchange server and it has a few other
bad habits configured into it which cause numerous other bounces to happen.
The solution was to block all null senders with matching fingerprints
from inside the network. I currently accept but freeze them. After 72
hours, I wipe them from the queue, just in case there's a legitimate one
and I happen to look at the queue in that time. Haven't found one legit
one yet.
Since doing this, they haven't been blocked once, and they haven't
received one complaint. They haven't lost any business, and the world
hasn't fallen off it's tilt. It seems X, Y and Z were not all that
relevant after all.
I freeze anything that comes from inside the network with a subject that
says "Out of Office AutoReply" in whole or in part. I was blocking all
<> senders but these turned out to be quite benign compared to OOR.
