Debian package outdated?

[Martin]

Glenn Steen wrote:

> quite a bit, version-wise. Jules has a debian package on his pages,
> but i think you need dpkg it... Or can one set that as a separate apt
> repository?

Since we're talking about versions here, why is the Debian package only 
at 4.51.5-1 (link on mailscanner site is pointing to Debian unstable)? 
There are many versions released after this one.

Anyone?