Operation Not Permitted
=======================

---%<-------------------------------------------------------------------------
imap(user): Error: chown(/home/user/mail/.imap/INBOX, group=12(mail)) failed:
Operation not permitted (egid=1000(user), group based on /var/mail/user - see
http://wiki2.dovecot.org/Errors/ChgrpNoPerm)
---%<-------------------------------------------------------------------------

This means that Dovecot tried to copy '/var/mail/user' file's group (mail) to
the index file directory it was creating ('/home/user/mail/.imap/INBOX'), but
the process didn't belong to the mail group, so it failed. This is important
for preserving access permissions with <shared mailboxes>
[SharedMailboxes.txt]. Group copying is done only when it actually changes the
access permissions; for example with 0600 or 0666 mode the group doesn't matter
at all, but with 0660 or 0640 it does.

To solve this problem you can do only one of two things:

 1. If the group doesn't actually matter, change the permissions so that the
    group isn't copied (e.g.'chmod 0600 /var/mail/*', see
    <MailLocation.mbox.txt>)
 2. Give the mail process access to the group (e.g. 'mail_access_groups=mail'
    setting). However, this is dangerous.It allows users with shell access to
    read other users' INBOXes
    [http://dovecot.org/list/dovecot-news/2008-March/000060.html].

(This file was created from the wiki on 2019-06-19 12:42)