Fighting spam via greylisting

USM Bish bish at airtelbroadband.in
Thu Apr 26 07:24:55 PDT 2007


On Wed, Apr 25, 2007 at 09:08:48PM +0200, Felix M. Palmen wrote:
> * USM Bish <bish at airtelbroadband.in> [20070425 20:43]:
> > 
> > OTOH,  Err Code  450 is  "Request mail  action not  taken:
> > mailbox unavailable"  (which is  perhaps what you  mean by
> > saying "user  not active now").  This is a  serious error,
> > and  indicates  ATRN  request  has  been  *refused*.  MTAs
> > compliant with RFC 822, should not respond this.
>
> That's  wrong.  Every 4xx  code  is  considered a  temporary
> error, and  sending MTAs  /should/ retry,  but they  are not
> required to do so.
>
> Only  the  5xx  codes  are used  for  permanent  errors  and
> indicate   that  the   sender  must   not  retry   the  same
> transaction.
>
---end quoted text---

Thanks  Felix  for  pointing  this out.  Somehow,  I  had  the
impression that 450  had the same implications of  550 !!! Its
never late to learn ;-)

Bish




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