[nzlug] (OT) Sorbs etc, was Exim: Limiting outgoing connections on Debian

[Daniel Pittman]

Cliff Pratt <enkidu at cliffp.com> writes:
> Donald Gordon wrote:
>> On Fri, 06 Oct 2006 15:12:37 +1300, Tony Wills <ajwills at paradise.net.nz> wrote:
>>
>>> I still get tons of SPAM via my ISP (although the amount that
>>> they're syphoning into the Spam folder at their end seems to have
>>> diminished).  I get none through my own server which uses
>>> greylisting - a very effective idea for small email servers - I get
>>> an awful lot of "unexpected disconnectsion"s from spammers that are
>>> asked to wait :-)
>>
>> Greylisting is not terribly wonderful.  It cuts down on some spam,
>> but breaks an expectation that many users have: that their email is
>> sent instantaneously.  And I have a client whose odd Mac-based
>> mailserver package doesn't know what retrying is :-(
>
> Greylisting is an evil perversion of the SMTP protocol and if I find
> any servers using it I blacklist them. Nasty obnoxious bandwidth and
> spool space wasters!

I don't think that word means what you think it means...

The SMTP protocol defined soft error cases specifically because there
*are* cases where a later attempt to deliver the same message will
succeed.

The traditional examples were a host that had mail down for maintenance,
a mailbox over quota or a site that was under too much load.[1]


So, whatever else greylisting may be, it is *not* a perversion of the
SMTP protocol.  It is, in fact, a use of the SMTP protocol as designed.

That fact doesn't contribute anything to the debate on the use of
greylisting, but neither do false claims about "perversion" of
protocols.

Regards,
        Daniel

Footnotes: 
[1]  Sendmail would respond with a 4xx code to reduce work for itself if
     it believed that the system was doing too much at the time.
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