On Friday 04 April 2008 21:45:11 SM wrote:
> MS Outlook and a few other MUAs support it. There's an option to
> split a message into several parts. [...] It's a useful feature
> if you want to get around message size limits to send attachments.
> It can also be handy when there's poor connectivity.

Right. The bad news is that many users of MS Outlook do not have
this option disabled, and every larger document or picture they send
gets split into chunks, whithout them being aware of it, and without
their correspondents using the same MUA having problems with it,
so this becomes a way of life.

The filtering-side bad news is that (as noted) the filter can't
do much about parsing it, and what is worse for SpamAssassin
users is that it takes substantially longer to scan these chunks
than regular text mail, letting regexps in rules try to make some
sense out of these seemingly random letters. A stream of such
messages can bring SpamAssassin down to its knees in no time.