multi sync (>2 servers) + selective sync + trigger

Hi all,

I've been researching ways to replicate mail across multiple mailstores and have a few questions.

Synching 2 mailstores (M1 & M2) via dsync works fine. I want to add a 3rd and 4th (M3 & M4) server to also be synced.

Multi-sync (>2 servers):

1. How do I tell M1 and/or M2 to also sync to M3 and/or M4?

Selective sync:

2. How do I sync specific domains to specific servers and not to others?

Trigger:

3. Does a normal sync check only check the mailbox being changed or does it get triggered on mailbox changes to check ALL indexes and sync all changed mailboxes accordingly?
4. Can I use an email to trigger a sync for any other mailboxes which might be out of sync?

TIA

B