[CentOS] Bounced email processing

[Valeri Galtsev]

On Wed, November 5, 2014 7:39 am, Les Mikesell wrote:
> On Wed, Nov 5, 2014 at 3:55 AM, Hugh E Cruickshank <hugh at forsoft.com>
> wrote:
>>>
>>> just parse the *maillog* instead
>>
>> That would only be effective for bounce messages that were generated
>> by our mail server (in the case of messages that were immediately
>> rejected by the foreign mail server when our mail server attempted to
>> hand the messages off). It would not work for messages that were
>> initially accepted for delivery but were subsequently returned as
>> being non-deliverable.
>
> Are there still servers that accept undeliverable mail and generate
> messages later?   That behavior makes them an easy target for spammers
> who send the real target address as the From: entry and will likely
> get them blacklisted.

Indeed, there are, and this sort of spam is called "backscatter". No need
to mention that like almost everybody else I have my servers configured so
that before deciding to accept message for delivery the server queries
next server if further forwarding is involved, and depending on answer
(deliverable/not deliverable) accepts or rejects message. This way we,
even when handling forwards, will not become source of backscatter. I do
have do make exemptions and if next server "lies" (says deliverable, then
when message is passed to it it is accepted, but later server sends non
delivery response), then I never let forwarding to these servers/domains.
Even for real users who moved there. Period. I had an interesting comment
from my friend about one of my exceptions. This exception is gmail.com
(who at least at some point were accepting everything, then were sending
you message: "user doesn't exist"). His comment was: hey, they are in
business of collecting information. Of course they accept everything. And
once they have the information, then they treat it as an e-mail message
;-)

Valeri

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Valeri Galtsev
Sr System Administrator
Department of Astronomy and Astrophysics
Kavli Institute for Cosmological Physics
University of Chicago
Phone: 773-702-4247
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