Keith Moore <moore(_at_)cs(_dot_)utk(_dot_)edu> writes:
It's been one of my long-running gripes with the DSN standard that the
from address should be a deliverable e-mail address.
I suppose the alternative is to provide no feedback path in case the
DSN was issued in error? I'm not sure this is better than the current
situation.
I can't say that I remember getting a useful mail problem report from
someone external to the institution rather than having the user who's mail
is having trouble notice it first.
Personally I don't see many human-originated replies to DSNs;
Lucky....
I don't see any or hardly any for the little domains I run for myself, but
postmaster(_at_)stanford(_dot_)edu gets quite a few of them even without a
repliable
address on our bounces. Before I made that change, we got lots, enough
that the people who were handling the address before I started fiddling
with it were complaining about it.
I think this may be one of those small site / large site discrepencies,
where once your mail volume hits a knee in the curve, you suddenly start
seeing a lot more of something.
I do see occasional replies/responses to DSNs from broken mail robots,
Yup, get those too. Some of them here in fact. I need to track a few of
those down and offer our central autoresponder service instead.
and *lots* of bounced DSNs resulting from spam that was sent to my mail
system, forwarded to another address, bounced, and couldn't be returned
to the original return address because it wasn't valid.
*sigh* Yeah. I'm tempted to filter all of those out, but occasionally
they point out problems like open relays that really need to be dealt with
right away.
I'm tempted to put in code that insists that all mail forwarded to
another system have a return address that appears to be capable of
receiving bounced mail - on seeing a RCPT to a forwarded address, it
will send HELO/MAIL FROM:<>/RCPT TO:<return-path> back to the MX for the
return-path address. If that gives me a 5xx response, then the response
to RCPT on the incoming message will also be 5xx - invalid return
address.
There are places where I'd definitely *not* want this (systems that are
mostly leaf nodes and forward their administrative mail to other systems
including their double bounces, for instance), but in general it's not
that bad of an idea.
--
Russ Allbery (rra(_at_)stanford(_dot_)edu)
<http://www.eyrie.org/~eagle/>