thunderbird?

[Mark W.]

I have Ubuntu 5.10 and would like to use Thunderbird instead
of the default mail client.

After downloading mozilla-thunderbird_1.0.7-0ubuntu1_i386.deb
to the home directory and running - in the same directory:
sudo apt-get install mozilla-thunderbird_1.0.7-0ubuntu1_i386.deb,
all I get is "Cuoldn't find package mozilla-thunderbird_1.0.7-0ubuntu1_i386.deb

What am I doing wrong? Is there another way to get Thunderbird mail client
onto Ubuntu 5.10?

tia,
Mark W.