"LISTSERV site administrators' forum" <[log in to unmask]> 
wrote on 06/24/2005 04:26:31 PM:

> On Fri, 24 Jun 2005 13:31:52 CDT, Anne Toal said:
> 
> > I guess I should have asked my question more concretely: is any of the
> > backbone traffic so time-sensitive that temporarily bouncing it will 
cause
> > Listserv to break? I'm not only concerned for my own server but how it 
might
> > affect the backbone traffic.
> 
> Umm.. X-SPAM announcements are fairly time-sensitive - the usual 
> "non-subscriber
> posts wait 10 mins" is predicated on the idea that if the spam 
> detector goes off,
> you'll find out in less than 10 mins.

Most greylisting implementations remember previous sender/receiver 
combinations, so after the first message, it should let future messages 
sail through without delay.  Check with the manager of the greylisting 
server.