On 23 Jul 2016, at 02:28, Apollon Oikonomopoulos <apoi...@debian.org> wrote: > > Hi, > > On 18:05 Fri 22 Jul , Timo Sirainen wrote: >> That would be a dangerous change. Users with shell access could >> symlink (or hardlink) other peoples' inboxes to their own folders and >> read them. > > IIUC, a more secure approach here would be to set mail_privileged_group > to 'mail' and leave mail_access_groups unset, correct?
mail_privileged_group is only used for creating dotlock files. http://dovecot.org/list/dovecot-news/2008-March/000060.html has some more explanations of this issue (mail_extra_groups was renamed to mail_access_groups). I added the same link now to http://wiki2.dovecot.org/Errors/ChgrpNoPerm Dovecot isn't really compatible with having mbox files being 0660 mode and having a shared (mail-)group. If the mode can't be changed to 0600, I don't think there's much that can be done now. I think it'll still work even though it logs errors about not being able to change ~/mail/.INBOX/* files' group? So what might be a possibility is to just not log that error if it's happening specifically to mbox INBOX.
