Sieve: failed to store into mailbox 'Junk': Mailbox doesn't exist

Hi,
I have a problem with the default configuration of the mail server, for users that never logged in through the IMAP interface (with Roundcube or any other client, their mails are just forwarded to another address) : some auto-created folders are never created, so Sieve filters fail to execute and generate log errors:

dovecot: lda(theuser@domain.tld): Error: sieve: execution of script /etc/dovecot/global_script/dovecot.sieve failed with unsuccessful implicit keep: 1 Time(s)
dovecot: lda(theuser@domain.tld): Error: sieve: msgid=<redacted_msgid>: failed to store into mailbox 'Junk': Mailbox doesn't exist: Junk: 1 Time(s)
dovecot: lda(theuser@domain.tld): Error: sieve: msgid=<redacted_msgid>: failed to store into mailbox 'junk': Mailbox doesn't exist: junk: 1 Time(s)
dovecot: lda(theuser@domain.tld): msgid=<redacted_msgid>: save failed to open mailbox junk: Mailbox doesn't exist: junk: 1 Time(s) 

Is there any solution apart from forcing users to connect at least once with an IMAP client ?

Hi,
From the dovecot documentation this seems to be the only supported behaviour.
http://wiki2.dovecot.org/MailboxSettings
"The autocreated mailboxes are created lazily to disk only when accessed for the first time."

A workaround would be to use yunohost hook to create the folders (post_user_create IIRC).