I can mail a podcast to myself and get it on my iPod.
The message comes through right away, then I have to click on a link
in the message to download the attachment.
But if I go back to an older message, where I have previously downloaded
the podcast, it is gone and I have to do it again.
Where are these files stored, how long do they last, and how can I move
them to somewhere permanent (like the iTunes library).