One mailbox server is active and does all the mail work: reading mail, delivering it, and checking passwords for sending. The others stand by, and if the active one goes down all of that moves to a standby together. paths lists those mail services and their ports, and note explains the arrangement.
Good to know
healthy means the server's agent checked in within the last 3 minutes; it doesn't test the mail service itself.
role is the planned layout from the api's own settings, not a live reading: if the mail service fails over by itself, this still names the old server as active.
last_heartbeat is null for a server whose agent has never checked in.
