Syncing Users and Homes from multiple virtualmin systems

Hey, I have 4 systems running virtualmin, (3xHTTP/HTTPS only / 1x Mail Only). I'm currently using LDAP for users, and NFS for the home. Is there a way I can sync users and the homes together into 1 NFS share so the the Mail server doesn't conflict with the already created domain on the Web servers? as long as the domains are different I've no problem with the multiple web servers, but the moment I create the same domain on the Mail server all hell breaks loose. Thanks in advance for any help.