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Re: People forging their From: addresses

  • To: Piet Beertema < >
  • From:
  • Date: Wed, 30 Sep 1998 12:48:11 +0200

>     For a while, I tried returning a 500 code, but I found that
>     the DNS is flaky enough to actually provide false answers now
>     and then, so I ended up rejecting a few messages a day who
>     were otherwise perfectly legal (out of like oh 100k per day).
>     So we switched back to 400 replies, so now the occasional mail
>     gets delayed a bit because it gets an "unfair" 400 reply, but
>     that's better than rejecting that mail altogether. Spammers
>     will usually not retry even with 400 style replies when
>     they're sending directly, and relays stop after a few days...
>     it's bearable.
> The latter remains to be seen. Originally I used 400,
> but I found that it only led to massive and almost
> endless retries for obviously bogus domains. Then I
> switched to 500. And the loggings show that really
> existing domains are hit only very rarely.

Very rarely becomes 'quite a lot' if you have hundreds of thousands of
emails a day. If 20 valid emails get bounced by us a day, that is unacceptable.
We can not put the burden of this on our users, so we have to bear it
ourselves by returning 400. This is partly ofcourse a difference in the
customers we serve :) And upto now like JP said, for us its bearable.

Ofcourse, we have a pretty strict AUP. If we notice a spam going on from
one of our users (who are ofcourse the only ones allowed to relay through
our mailservers) then the chances are high they need to find themselves
another ISP.


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