Milter-greylist

> If above scenario were repeated, the first email M1 whould not
> delivered and finally bounces to the sender. Lesson: autowhitelist
> should have enough long lifetime, for example 5 days.

This kind of thing is one of the reason I proposed not to have two
separate list: one for autowhite and of for pending in my mail dates back
to 21st of October 2005.

Bests,
Attila