We may want to go on ZCS but I'm not sure migration can be done.
In fact, the existing LDAP is used in order to:
1) Authenticate users on Linux boxes
2) Authenticate users on applications
3) Authenticate users on mail (based on OS)
4) Retrieve valide email address. On user can have more than 1 address and 1 address can be set on more than 1 user
5) Set groups for Samba access
6) Limit specific URL access
So we need to keep the ldap and connect Zimbra to it.
Question is: how to create/authenticate users and set mail address using actual LDAP