[Evolution] Can I tell evo that my IMAP server is local?

[Randy Orrison <randy orrison com>]

I'm using an IMAP server to access my mail files; the files and server
are both on my local machine.  Evolution apparently caches the headers
of all messages, and bodies of opened messages; the cache takes up more
space than the mail itself:

$ du Mail/ | tail -1
23204   Mail
$ du evolution/mail/imap | tail -1
24284   evolution/mail/imap

Is there any way that I can tell evolution not to bother caching the
bodies and headers of mail that's is itself local?

Thanks!

Randy