Hi.

> I have 10s to 100+ mailboxes hierarchically organized.
> I have close to 600mb and 90,000 messages in mail.
> I would love for Celeste to be able to handle that.

Fidonet had nice stuff to hold tons of mail efficiently, especially the
Squish and Jam mail storage designs.  I believe that I have the
standards somewhere, they seem pretty straightforward to implement. 
Among other things, Squish supports mail file compaction on the fly
while storing new mails.

Andres.