Dear Timo,

we have successfully used dovecot-shared file flag in Maildir Public NameSpaces with private index files, to have per-user-seen flags for some but not all mailboxes under public folders.
This was actually done on older dovecot versions (i.e dovecot v2.2.33.2) , using a location setting in dovecot.conf like:
location = maildir:/var/vmail/PublicFolders:LAYOUT=fs:DIRNAME=privDirMailFolder:INDEX=~/Maildir/public

We try to use similar location setting using sdbox storage in dovecot v2.3.4.1, like below:
location = sdbox:/var/vmail/PublicFolders:LAYOUT=fs:DIRNAME=dbox-MailFolder:INDEXPVT=~/Maildir/public
but the dovecot-shared file flag seems to be ignored.
As a result all mailboxes under public folders use the per-user-seen flags setting as set in the location setting, regardless of the existence of the dovecot-shared file flag or not.

Is there any setting to use so that only some mailboxes under public folders use per-user-seen flags?

Thank you in advance for your support,

Panos Fafakos.