Milter-greylist

Some ideas for the next milter-greylist release.

Idea one
========
Some users complains sometimes about greylisting delays. Milter-greylist
allow many
ways to satisfy them but it needs to modify greylist.conf and restart.

So a good (or a bad) idea could be to give the senders some control on
the delay
by adapting the waiting time (option -w) according to the X-Priority
header (needs to inform senders to be efficient) of icoming mails.

Thunderbird allow us to define the following priorities :

X-Priority: 1 (Highest)
X-Priority: 2 (High)
X-Priority: 3 (Normal)
X-Priority: 4 (Low)
X-Priority: 5 (Lowest)

MicroSoft use 

X-MSMail-Priority: High
X-MSMail-Priority: Normal
X-MSMail-Priority: ...
...

So having in greylist.conf

greylist 15m

and take care of priority with 

priority_highest    -13m
priority_high       -10m
priority_normal     +0
priority_low        +45m
priority_lowest     +4h

(I dont know if it's better to give relative or absolute value)


Idea Two
========


Many spam come now as a gif, jpeg or png containing text. If we apply
the same idea as above delaying longer by adding a new delay to the
previous one when a mail come with attachements

ct_gif_add	1h
ct_jpeg_add	30m
ct_png_add	5m
ct_htm_add	5m
ct_doc_add	5m


It needs to scan the body searching for :

Content-Type: image/gif
Content-Type: image/jpeg
etc.