[nSLUG] Whither to bounce unknown recipient address?

D G Teed donald.teed at gmail.com
Thu Aug 30 23:59:37 ADT 2007

On 8/30/07, Aaron Spanik <a.spanik at ns.sympatico.ca> wrote:
> On Thu, 30 Aug 2007 13:16:15 -0300
> I can't decide whether it sounds like things have changed since I last
> saw the configuration you're looking at ;)

Not that much change, just tweaks and minor upgrades.
Biggest one is dropping SORBS and going only
with commercial RBL+ which is like night and day.
Block lists really need someone taking care
of that data maintenance as a profession, in my opinion.
We did try SORBS alone for a few months.

> I would point out, however, that I suspect
>         unknown_local_recipient_reject_code = 550
> will have no effect whatsoever unless you're setting it on the mailbox
> server (and I'm pretty sure you wouldn't be).  So I believe the setting
> you're actually interested in is one of
>         unknown_virtual_alias_reject_code = 550
>         unknown_virtual_mailbox_reject_code = 550
> and the default appears to be 550 for both of them.

postconf has revealed lots of defaults for reject_code which are
good ones. I should have looked at that earlier.
A postfix developer says other reject_code vars will handle
other bounce types I'm concerned with, so that is OK.

I'm not 100% that this reject + bounce from the other relay
will prevent back scatter.  If my spam bot is on eastlink cable, and
I sendmail out, providing hotmail.com or gmail.com as my from address,
smtp relay on eastlink sends back a bounce rejection to my hotmail
or gmail address after being told the recipient party SMTP rejected due to
non-existent recipient.  All it does is shift the source of the
back scatter by one SMTP relay.


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