[Mailman-Users] Removing attachment

Brad Knowles brad at stop.mail-abuse.org
Tue Feb 22 23:01:02 CET 2005

At 1:43 PM -0800 2005-02-22, Allen Watson wrote:

>  It really would be so much better if there were a simple setting to
>  reject ALL messages with attachments, as some other mailing list
>  software provides. It can't be so difficult...

	Actually, yes it is.  MIME bodypart types come in pairs, and 
there are an unlimited number of potential combinations of these 
pairs.  Moreover, there are also a variety of other 
attachment/encoding techniques (uuencode, binhex, etc...) which do 
not depend on MIME at all, and in fact would look to the program just 
like normal ASCII text.  Indeed, the entire purpose of many of these 
alternative encoding techniques was to be able to survive being 
transmitted via 7-bit ASCII-only transmission networks, such as can 
be provided by e-mail.

	And don't get me started on steganography.

	Given that there are an unlimited number of possible encoding 
techniques, it is physically impossible to block them all.

	This is why Mailman provides the tools that it does, and it 
allows you to choose to either filter out the stuff you know to be 
bad (allowing through everything else), or to allow through only the 
stuff you know to be good (filtering everything else).

	This problem is much more complex than you give it credit for. 
Do Internet e-mail systems administration for a decade or two, and 
you'll find that there are all sorts of bizarre things out there that 
you never thought could possibly exist.

	Mailman can only deal with those things that it knows about, and 
we've given you powerful tools that will help you solve most of the 
problems, if you use them correctly.

Brad Knowles, <brad at stop.mail-abuse.org>

"Those who would give up essential Liberty, to purchase a little
temporary Safety, deserve neither Liberty nor Safety."

     -- Benjamin Franklin (1706-1790), reply of the Pennsylvania
     Assembly to the Governor, November 11, 1755

   SAGE member since 1995.  See <http://www.sage.org/> for more info.

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