deleting trash files/attachments for good

I just recently bought my nokia and it seems to work fine except that
the built in mail program seems to leak trash files and attachments all
over the place. I know how to delete messages from a symbian phone
(select delete phone and server and delete messages from remote server
too and then going online on the phone again to get rid of headers) but
for the second time now I find an attachment -that was deleted and did
not show up in the mail program anymore- still saved in the phones
memory. (I had to download Fexplorer to find and delete it).
Also there is a subfolder Mail in the folder system on the phone and
the MMC Card (only visible on Fexplorer) with a lot of empty files that
look like 0100001b, 00010000s and so on.

A) Can I delete those files without frying my phone?
B) How can I prevent my mail program (not third-party, it is nokias
original application) from leaving files hidden in the memory after
deleting them?
C) Is there an application for the nokia that seeks out trash files and
deletes them by itself (I myself have no idea if I am dealing with a
trash file or not?

Please help!