Delivery time expiration

[John Mason Jr]

David Cary Hart wrote:
> 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.


Actually in a live system with greylisting implemented I found that 
email was accepted in well under 5 minutes. And that was before 
whitelisting, admittedly this was an corporate email system so the 
majority of ham was from a relatively small number of servers.


> 
> 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.
> 

As with any other server/service the devil is in the details, properly 
implemented greylisting will not be noticeable to the end user.


John Mason