4.40.5: IPBlock 451 versus 550
t.d.lee at DURHAM.AC.UK
Thu Mar 17 15:05:46 GMT 2005
On Wed, 16 Mar 2005, Julian Field wrote:
> David Lee wrote:
>> The idea seems to be to return a 4xx-like failure to connections from
>> hitherto new/unknown places, and notes that the connection attempt has
>> been made ("if I haven't met you before, then 4xx."). A large proportion
>> of spam engines simply won't bother to retry.
>> By contrast, legitimate email (yes, and some residual spam) would always
>> try again a few minutes later, and so when it does, this time the call is
>> accepted ("I've just met you, so I accept you 200-like").
> Very interesting idea. I will have a think. Unfortunately I would have
> to accept the first mail in order for it to get into MailScanner at all.
> And that may defeat the idea altogether. Any thoughts?
Of course. (Hits self over the head with clue-stick.) And thanks to a
couple of other folk who also kindly showed me the obvious (and to yet
others who showed that it might have bad side-effects on some perfectly
legitimate sending ISPs).
: David Lee I.T. Service :
: Senior Systems Programmer Computer Centre :
: University of Durham :
: http://www.dur.ac.uk/t.d.lee/ South Road :
: Durham :
: Phone: +44 191 334 2752 U.K. :
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