Feature Request: Header based rules..

[Dhawal Doshy]

Hello List,

Any thoughts on adding header based rules? say for example:

spam.check.rules:
header X-MyLocalApp no

OR

virus.scanning.rules:
header X-Cron no

OR
use.spamassassin.rules:
From: mydomain.tld and header X-Auth-MyServer no

If there is sufficient interest, maybe Julian might find the time and 
energy to take it up.

- dhawal