[exim] mime_filename and &# encoding

Damn spammers.

We implemented this a few weeks ago to great effect:

deny message = Blacklisted file extension detected
   condition = ${if match \
                    {${lc:$mime_filename}} \
                    {\N(\.exe|\.pif|\.bat|\.scr|\.lnk|\.com|\.zip)$\N} \
                 {1}{0}}

It has hugely reduced the amount of spam, but they have suddenly worked
around it by sending documents with an attachment name of "& # 1057 ;
opy_of_document_SER176.zip" (without spaces)

which with the character encoding seems to evade the $mime_filename check.

Any suggestions as to how to fully block ANY file with a zip extension,
regardless of the encoding in the name?