if you are worried about this script filling up some disc, then you are in serious problems.
even if it had to process hundreds of files the text files wont go over a few kbs
you have to star talking about thousands of files to get something like 1mb
actually. i did some tests.

if your script encoutnered arround 5thousand files to be moved (that implies temporal files containig the body of the mail to have 5thousand lines)
and each line beein 76 chars long (wich is several subfolders long)
the temporal folder would be still under 400k

but, if youw ant to keep track of how much a folder or file is worth in kb, i suggest you to search the forums.
i know there must be at least 5 similar quesiotns on the last week