Thunderbird and local mail ?

[FreeBSDBeni]

Hi,

System: 5.3-REL-p5

I would like to get my local mail (from /var/mail/<user>) in my 
Thunderbird (v1.0 - 20050310) mailbox.

I found 
http://lists.freebsd.org/pipermail/freebsd-questions/2003-December/027652.html 
which is talking about version 0.3... But I get the same message as 
described after having created a movemail mailbox : "unable to create 
<user>.lock file". I've tried to set up a movemail for the user and one 
for Root, but get the same message back.

So, how do I get those local mails transferred into my mailbox ?

Beni.