[Dovecot] Maildir owner importance

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) ?