[Dovecot] Maildir owner importance

[Roi Efrati]

I have set up a directory (/var/local/virtualdir/) as the maildir with
a special user/group (virtualmail) and in it I create directories for
each domain (example1.tld, example2.tld etc) and sub dir's for each
mailbox). Only at the moment, apart from the first one, they are all
created as with user root as the owner.
How important is to have all the directory tree owned by the same user
group (virtualmail:virtualmail) ?