[Exim] mode 660 / maildir / parent directory set as 700

I have the following tranport as i intend to host imap for a number of
domains on this server

whenever a valid user receives an email, the maildir directory is created
and the messages with mode 660

however, any parent directories created int the proces of delivering a mail
are created as user=exim and group=mail but in mode 700.

My next quest is to compile cyrus-imap (maybe as user=cyrus, group=mail),
but that would require group 'rwx' rights on the parent directories. Any
suggestions?

# ----- intranet-mail transports -----
intranet_local:
driver = appendfile
directory = /var/spool/virtmail/$domain/$local_part/maildir
delivery_date_add
envelope_to_add
return_path_add
maildir_format
group = mail
user = exim
mode = 660
prefix =
suffix =
check_string =
# ----- intranet-mail transports -----

The directors i'm using to 'capture' virtual users are

# ----- intranet-mail directors -----
intranet_aliases:
driver = aliasfile
search_type = lsearch
domains = lsearch;/usr/exim/etc/intranet.domains
file = /usr/exim/etc/$domain.aliases

intranet_local_users:
driver = smartuser
domains = lsearch;/usr/exim/etc/intranet.domains
local_parts = lsearch;/usr/exim/etc/$domain.users
transport = intranet_local
no_more
# ----- intranet-mail directors -----