solution is to install GNU mailutils/movemail and add a movemail account to thunderbird
Seven years later, it helped me out too.
I had to separately install a Ubuntu package called 'mailutils' which includes an executable called 'movemail'.
Once done, Thunderbird started offering the 'movemail' option for a local mail-accont.
Still dismaying to find out that Thunderbird can't support a simple concept like a local file folder for incoming email out of the box.
Last edited by benteveo; 11-11-2012 at 02:25 AM.
Reason: correct package name