Delivery time expiration

[David Cary Hart]

On Mon, 13 Feb 2006 17:45:45 -0500
"Scot L. Harris" <webid at cfl.rr.com> opined:
> 
> Remember greylisting uses standard RFC rules to defeat spam.  It sends a
> 451 error on the first attempt which means there is a temporary failure
> please try again later.  After the greylisting timer expires any message
> coming from the same IP address with the same sender and recipient
> (tuple) will be allowed through.
> 
> And for those that claim their emails are hyper important it would
> benefit everyone to place a phone call to verify receipt of such an
> important email.  
> 
Come on. That's hyperbole in support of a concept. I have no problem
with greylisting unfiltered roll accounts (eg postmaster and abuse).

However, the actual delay varies depending upon the cycle of the
retransmit timing and the greylist timing. It is often necessary to
re-transmit 451s several times which means that the recipient server
and the SMTP are both consuming cycles and bandwidth.

Furthermore, while the administrator of the recipient server might
embrace the notion that email is not - and should not be - regarded
as spontaneous, the average business sender is not thus inclined. He
or she expects that his or her transmission will be read immediately
in many cases.

Taking it a step further, many business emails are group discussions
with several recipients necessitating spontaneity. If one recipient
has the bad luck to be on a greylisted server, it affects the group.

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