Version:           1.9.3 (using KDE 3.5.3 Level "a" , unofficial build of SUSE )
Compiler:          Target: i586-suse-linux
OS:                Linux (i686) release 2.6.16.13-4-default

for opening an attachment a temporary file is used.

IMHO for saving such a file, the original name should be restored and the default location should be proposed.

it does not make sense to store the document in the temp area.

if the problem could be solved in the kfile module it could be also used by OO and others.

all file names seem to be extended and 
start with:
/tmp/kde-<LOGINNAME>
and end with:
_[<random extension>].<doctype>

so converting to a meaningfull name should be possible.