[Dovecot] New mailbox format

[Cor Bosman]

> > inodes only use kernel memory when the file is accessed. in this respect there
> > is no difference in the memory usage between reiserfs or ext3 or any other
> > filesystem. think about the case of network filesystems for example.
> 
> i think we're agreeing aren't we?
> 
> the only reason i care about kernel memory usage is that once you start 
> scaling to 1000s of simultaneous users kernel memory starts becoming 
> scarce... with maildir it happens a lot faster than with mailbox.

Anyone that scales to thousands of simultaneous users should be able
to afford a few extra servers and has a server architecture where adding
servers is easy. 

Cor