Milter-greylist

Oops, hotmail et al fire on that as their servers are (erroneously?)
detected as "Windows 2000 SP4, XP SP1+" ...

Solution:  put this before the p0f stuff:

list "bypass spfs" domain { hotmail.com microsoft.com }
racl whitelist list "bypass spfs" spf pass

The more reliable workaround is to remove this line:

> racl greylist p0f "Windows 2000" delay 20m autowhite 14d \
>   addheader "X-Greylist-OS: %Fx"

And thus only greylist Windows XP when it is detected without a chance
of Windows 2000 (yes, this does happen, though it's rarer).