Slightly OT: Greylisting success or failure stories?

Scot L. Harris webid at cfl.rr.com
Fri Feb 4 02:31:13 UTC 2005


On Thu, 2005-02-03 at 21:12, Jeff Kinz wrote:
> On Thu, Feb 03, 2005 at 09:03:24PM -0500, Scot L. Harris wrote:
> > On Thu, 2005-02-03 at 20:34, Jeff Kinz wrote:
> > > 
> > > It is inadvisable for anyone using email in a professional capacity 
> > > to use any form of TMDA (whitelisting/greylisting).
> > 
> > Interesting rant.  And I agree with most of what you state about TMDA. 
> > I refuse to respond to such requests.
> > 
> > However don't lump greylisting in with TMDA.  
> 
> Point taken. The exact definitions of what constitutes "whitelisting,"
> TMDA and greylisting have shifted continuously since their recent rise
> in popularity.
> 
> But -according to a Google definition lookup - You are right.
> Greylisting is not a form of TMDA.  Quote:
> ############################################################
> 
> Greylisting 
> How it Works

<snip>  Good explanation of how greylisting works.  :)

> 
> 
> This leaves the possible remaining objection centered around exactly
> how long the email will possibly be delayed for, and/or the possibility
> that some email systems mail never retry. (poor ones ;-) )
> 

I have seen very little difference between setting a 30 minute or a 2
minute greylisting delay.  Other than starting with a 30 minute delay of
course. :)  

Of course the actual delay is controlled by how the sending MTA queues
and retries messages.  Based on the log files I have looked at most
legit MTAs retry a message several times in the first 5 to 10 minutes.  

MTAs that don't comply with the RFCs should be identified and removed
from the Internet.  If they don't respond correctly to a temp failure
code then they are subject to loosing email in other situations as well.

Probably the biggest problem is identifying server farms where a message
may be retried from a different IP address.  The greylisting
implementations I have seen generally start with a list of such servers
which are whitelisted and as such are not greylisted on the first
transmission.


-- 
Scot L. Harris
webid at cfl.rr.com

Quantity is no substitute for quality, but its the only one we've got. 




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