[Dovecot] Webmail architecture : questions about cache and storage backend

[forumer at smartmobili.com]

Hi,

I have some questions about dovecot-2.1 and need some advice about 
software architecture.
My company plans to develop a kind of Document Managing System (DMS) 
and one of its module is a webmail
that is currently in a pre-alpha stage (if you are curious you can have 
a look here
http://kairos.smartmobili.com/ but don't be surprised if it doesn't 
work and please
do not use IE for now).
 From my personal analysis that I am sure is incomplete we have the 
following options to handle
emails storage and cache:

1) Do not use a cache and rely on dovecot performance to retrieve 
email's header in real time.
    Actually don't know if it's that simple because we might need to 
have a transformed version
    of emails to be able to display them more easily in the webmail. In 
this case this option is
    not really possible.

2) Use new dovecot-2.1 imap backend and develop a kind of dummy imap 
server listening to a custom port
    and storing emails inside a mongoDB database. Advantage is it allow 
replication very easily.

3) Wait for dovecot2.x to implement a NoSQL storage. Will it happen 
soon ?

If you have other suggestions or ideas I would be happy to hear them.

Vincent R.