Sharing a single solr server between multiple dovecot servers

I am brand new to solr and I'm interested in using sharing it between several dovecot machines I'm running. I'm looking for some big picture guidance on what I need to do to configure solr to work with the different dovecot machines. So far, I managed to set up a single "dovecot" core on the solr server and it is working with one of my dovecot machines.

I'm not sure how to proceed from here as I'm very unclear on how solr maintains separate indexes for different users on my different machines. Some basic questions I have are:

1. Do I need a new core for each of the dovecot machines I want to use with solr?
2. If not, how does solr ensure indexes for the different dovecot user do not get comingled?
3. If yes, how do I configure dovecot to tell it which solr core to use?

Thanks.