Milter-greylist

I've been happily using milter-greylist for a few years, with pretty
great results -- spam level is barely noticeable, and I'm only using
greylist by itself at the moment.

Recently I've noticed again I'm occasionally missing messages, or at
least hitting multiple iterations of delays; when I dig into the logs
it appears to result from the sender using a mail relay server "pool".

E.g. the 1st delivery attempt comes from relay1.example.com, which then
gets greylisted; the 2nd attempt comes from relay2.example.com, the 3rd
from relay3, and so on.

In some cases a previous relay will get the message to try again, and
the message will eventually be delivered normally.

In other situations, possibly with very large relay server pools (?),
the autowhite timer for the relay(s) expires, and the sender eventually
gives up presumably due to their own retry policies.

I've noticed this happening a few times with domains hosted by office365
outlook.com, though I'd expect there are others.

When I notice these sort of issues, because it's a person or domain I
want to associate with, I simply add them to my white list as needed.

But I'm wondering if anyone has found a more automatic / elegant way
of handling situations like this.

Cheers,
sr.