Milter-greylist

> > I've heard users describe instances where mail is delayed for about a
> > day.

> the sending mailserver decides when it will do the next delivery
> attempt. You have no influence if or when it will retry.
>
> The cause may be high load, long mailqueue, bad configuration or many
> other things

okay, so that seems to allege that the problem isn't with
milter-greylist's configuration ... it is still a problem, and caused by
greylisting itself.  I've had to add a very large number of problematic
mail relays to the whitelisting section of my greylist.conf file.

Example:  gmail doesn't play nice with greylisting (as noted at
http://tinyurl.com/27ey2t ) so the fix is to traverse their SPF and
whitelist every named server (noted at http://tinyurl.com/2znyqh )  ...
other companies aren't as easily marked (lack of SPF plus the fact that I
have to do it on a case-by-case basis).

Is there a public exchange of servers that don't play nice with
greylisting that is larger than the default?

This is a large enough problem that I may stop using the milter, or
perhaps enable it only for hits in DNSRBLs.