Filtering on filename extensions

[Q G Campbell]

This site has chosen to use the default ~/etc/filename.rules.conf for
our roll out of Mailscanner.

One consequence of this decision is that attachments containing files
such as "proposal.rtf.doc" are now being blocked with an "Attempt to
hide real filename extension" warning message.

This occurs whether or not the .DOC attachment carried a virus and was
disinfected. I don't think it should have blocked simply because of the
filenames rules.

In particular I would expect a message with a repeated file extension to
be delivered, provided it passed the virus scan phase, _if_ the last
extension was ".DOC".

In the light of the above I would like to ask:

 1. Is it "safe" to modify filename.rules.conf in the way I have
suggested?

 2. If it is safe, what is the best way to modify the conf file to
achieve
    delivery of .DOC files.

 3. Why are common file extensions like .DOC ignored altogether in the
    filename.rules.conf file?

I carried out a sample survey at this site recently of more than 20,000
messages with attachments and almost 50% were .DOC files. Thus better
handling of .DOC files is an important issue for us.


Quentin
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PHONE: +44 191 222 8209    Computing Service, University of Newcastle
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