dovecot - Dec 2018 - dovecot user id and mail folder permissions, was "no shared cipher"

Greetings,

I thought it may be better to start a separate thread now that the
cipher problem is solved.

Background: I have had to recreate from scratch, and without notice, a
working server to a new VPS, with different versions of dovecot and
other software. Now I am having problems with accessing the imap
folders from home.

Now I have postfix/procmail successfully delivering email to the right
IMAP folders.
Problem is, postfix/procmail run as user mail_manager, group
mail_management, and the permissions on those folders are currently
all set to 755.

The consequence is that dovecot, running as user "dovecot", extra
group mail_management, cannot modify those folders and their indexes.

What is the best/safest configuration in these cases?

1) run dovecot too as user "mail_manager"? (if yes, how, with dovecot
2.2.36?)

2) recursively change permissions of ALL the mail folders and files to 775?

3) both 1) and 2) ?

4) other (e.g. certain permissions for folders, others for specific files?

Thanks in advance for any advice!

Marco