woody upgrade/update path

[Hans du Plooy <hansdp@newingtoncs.co.za>]

Hi all,

I have to install spamassassin (and likely some sort of virus filtreing - 
amavis or so) on a handful of debian woody mailservers.  Also, I need to add 
hylafax server to them all.

The servers can't go down, at least not longer than a restart if it really has 
to, so I have to find a way to update the necessary packages.

apt-get install gives me spamassassin 2.2, while I would like to have 2.6.x

So far I've need to upgrade libc6, tiff, perl (between spamassasin and 
hylafax).  apt-get doesn't automatically do these deps

What is the best and safest (as far as upgrading production servers goes) way 
to upgrade these machines?

Thank you
kind regards
Hans du Plooy