[Evolution] Disable IMAP cache

[Jérôme Warnier <jwarnier beeznest net>]

Is there a way to disable local IMAP cache in Evolution?

I'm using homes on NFS, so the IMAP server is as close to the end-user
as the NFS server. 
In this case, there is no need to keep a cache of the e-mails, and I
could offload the network quite a bit if it did not cache the e-mails.

Thanks