Was this ever updated? It still seems kinda all over the place. Maybe section off the instructions a little better based on need then include the options within that section? Something like...
If you want your primary Smartermail server to route outbound email through a secondary Smartermail server:
1) On your primary Smartermail server do this.
-For one or multiple domains
-For all domains.
2) On your secondary server do this.
If you want to setup a backup Smartermail MX server to receive email when your primary server goes down.
1) On your primary Smartermail server do this.
2) On your backup Smartermail server do this.
If you want inbound mail routed through a secondary Smartermail server then forwarded to your primary Smartermail server.
1) On your primary server do this.
2) On your secondary Smartermail server do this..