I am discussing about spli-domain and would like to know which approach would be easy and less painful for implementation? I have say example.com currently hosted on exchange where aroung 5000 users are configured, i would like to co-exist Zimbra along with Exchange and would want to move around 1500 users from there. MX is currently pointed to Postfix gateway Here is the topology
INTERNET ----> MX of example.com [mail.example.com]------> exch.example.com
1] Now for integrating Zimbra would it be feasible to deploy another postfix server just after the mailgateway and maintain LDAP DB and then configure LDAP based routing?
INTERNET ----> MX of example.com [mail.example.com]------> POSTFIX[smarthost.example.com]+LDAP---->exch.example.com OR Zimbra.example.com
2] Or is it easy to implement split-domain as specified in Wiki? But in that case Zimbra being Primary domain, dont you think creating mail boxes and route mails for more than 5000 users would be a hectic task?