hi devnul,
how do you currently authenticate the two samba-server's.
what we have done in a similar situation (two samba-server on two location's)
i am running on both side's a ldap-server (on ubuntu 8.04.1) replicate this two and authenticate samba against this openldap.
the user's get managed by gosa (
http://www.gosa-project.org), when a user get created in gosa with mail-attribute's gosa execute's a script (running with ssh on the zimbra-server, which is only on one location) and create's with zmprov the account with the attribute's out the ldap-server.
authentication within Zimbra is done against the openldap-Server, so zimbra, samba and unix-logon's are in one database.
it is necesarry the account-name's are the same in both part's (ldap, samba and zimbra, the domain-part cat get cuted off, when auth to ldap from zimbra)
this would be some work on the system, but pretty less on zimbra's side.
disadvantage: password modify cant be done in zimbra.
greetings
thomas