[Dovecot] Populating mailbox dir

[Mauricio Tavares]

	Let's say you created a (virtual) mail user but have not created the 
user mail directory. When you first try to access it, the mail directory 
is created and populated:

ls -a /var/spool/vmail/domain.com/raub/
.    dovecot.index.log    dovecot-uidvalidity.4d375a39  tmp
..   dovecot-uidlist      new                           .Trash
cur  dovecot-uidvalidity  subscriptions

Who populates/creates the initial files and folders in the user mailbox? 
Dovecot? The mail client accessing it through imap? Elvis? If dovecot, 
is there a way to customize it a bit, so a few extra folders will also 
be thrown there?