[Exim] Filter quotation marks in local_part

Some spammers use an error in LotusNotes to relay email to an adress
given as a local part in quotation marks to a local domain. e.g.: If
you send an email to "bob@??? and mycompany.cno is
your local domain, lotus sends the mail to bob@???.
Luckily our customers Lotusnotes server is protected by an exim-server
(Version 3.35 with Debian Linux) that proxies SMTP-connections. I do
now try to craate a filter, that prevents local parts witch quotation
marks to be delivered. My filter file looks like this:

# Exim filter
if $local_part contains \" then
save /tmp/spam
endif

The filter is correctly installed but the emails are still delivered if
an quotation mark is in the local part. Exim makes no difference
between "user"@domain and user@domain

Any ideas?

Best regards
Felix

--
Felix Havemann  -Leiter Technik-          w         f.havemann@???
n@work Internet Informationssysteme GmbH  o         http://www.work.de
Spaldingstr. 160d                         r  Tel.: +49 40 23 88 09 - 0
D-20097 Hamburg                           k  Fax:  +49 40 23 88 09 -29