[Mimedefang] early experiences with grey listing

David F. Skoll dfs at roaringpenguin.com
Thu Jan 13 11:38:00 EST 2005

On Thu, 13 Jan 2005, Gary Funck wrote:

> I'm now thinking there may be a hybrid strategy, where we shorten the
> initial blackout period to 1 min., and then if the sender does retry,
> we place it in a holding tank for 1 hour.  This would ensure ultimate
> delivery at least, and give time for the SURBL's to populate.  The cost
> would be a delay in delivery of some mail.  I don't know, however,
> how this might be implemented within MIMEDefang without tieing up
> a thread for each delayed mail processing event. Is there a method
> for locally requeinng for re-delivery 1 hour later?

You'd have to spool the mail into some other queue that gets processed
every so often, and set a MinQueueAge of an hour on that queue.  It
seems way too tricky to me.

One thing that most greylisting implementations don't do (CanIt does
it) that's essential to being a good Net citizen is to turn off
greylisting once you know a host retries.  It can be pretty annoying
for large sites to have their mail greylisted even though it's
perfectly obvious that their outgoing mail servers are going to retry.

In CanIt, once a server successfully passes the greylisting hurdle, we
turn off greylisting for that server for 40 days.


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