Add support for lazy loading folders when the user requests them. For instance in many Outlook environments there are lots of folders under the "Public Folders/" namespace. These are seldom used by the users and create the illusion of that kmail/kontact/akonadi doesn't support reading from an Outlook server (see http://lists.kde.org/?l=kdepim-users&m=132342358911548&w=2). As a solution to this (this also seems to be the default when using Outlook client to access the mailbox) would be to not load the folder contents until a folder is selected.
a) It's an obscure feature IMO; b) Volker just confirmed me you know how to implement it anyway. ;-) (in any case we can give you help in this endeavour) So exceptionally, I'll close this one as WONTFIX. :-)
Wasn't my request (just a submission proxy) so don't hold your breath :)