I'am using 6.40.7 on SME 7.5.1 for ca 20 users, using the unix-plugin (not the db-method). Every existing user and new user gets automatically a zarafa-account and mailbox.
groups and machine-names are not included in the address-book since one of the latest smeserver-zarafa-rpms (new unix.cfg-template that filters groups and machine-names out).
F.