That would require a server-side script to receive the e-mail, process
it and add the contents to your TiddlyWiki file.
The idea's quite nice, but I don't think anyone has implemented it yet.
If you're familiar with Ruby, you might look into r4tw:
http://www.tiddlywiki.org/wiki/Dev:R4tw
-- F.
That just might work - any volunteers?
-- F.