[Dovecot] load sbub-mailbox

[mourik jan heupink]

Hoi Daniel,

> Additional namespaces can be dynamically added via environment variables.
>
> Try to add the "oldspace" namespace dynamically using PostLoginScripting
> http://wiki2.dovecot.org/PostLoginScripting
> if an old mailbox is available for $ENV{'USER'}

Thanks very much for your kind help and assistance!

Mourik Jan