You'd think that reading mail in Thunderbird ought to be really easy - after all,
Thunderbird's a mail client,
that's what it's for.
But I'm talking about reading mail from inside of Javascript - getting access to the body of a given message.
This turns out to be a little more tricky.
First,
there is no object which corresponds directly to a mail message.
The best you've got is the nsIMsgDBHdr interface,
which corresponds to an email's header plus a few more useful bits of metadata.
From this you can find a mail's "key",
which is the internal value that Thunderbird uses to identify it,
its folder,
and from thence you can read its body.
