Bug/feature: mail fs pollution on IMAP select namespace/{non-existent}

[Timo Sirainen]

On 24.6.2014, at 16.04, Peter Benko <pbopbo at freemail.hu> wrote:

> I have noticed a strange behavior with dovecot (tested with 2.2.13). I use shared folders to share mailboxes between users. I have a namespace called "Accounts" that hosts the shared folder for the users (prefix Accounts/%%n/). However, When I issue an IMAP select command on a random non-existent mailbox name under "Accounts", dovecot auto-creates it and pollutes my mail root directory:
..
> mail_location = mdbox:~
..
> namespace {
>  list = children
>  location = mdbox:/mail/mailboxes/%%d/%%n:INDEX=/mail/mailboxes/%%d/%%n:INDEXPVT=/mail/mailboxes/%d/%n/indexpvt-accounts/%%n

location = mdbox:%%h:INDEXPVT=/mail/mailboxes/%d/%n/indexpvt-accounts/%%n

This forces Dovecot to do a userdb lookup for the user to get the home dir, which should fail if the user doesn't exist.