Think this just got worded wrong, sounds like he wants to do the following multi-server setup:
Server 1: LDAP, MTA, Store, Logger
Server 2: Store
To explain a bit: The mail Store is commonly referenced as Mailboxd = Jetty + MySQL + Lucene + etc > to provides services from http/imap/pop/caldav/carddav/webdav/activesync/mapi to even bundling in a bare wildfire xmpp server currently). The apache referred to in the installation prompts is used for the web-client's aspell checker. (Convertd package now also makes use of it.)
Organization dependent of course, but you could also consider putting the MTA separate:
S1: LDAP, Store
S2: MTA
If you've studied your
zmstats and know what you want go for it - though we could probably offer some advice from experience if you provided the number of users, server/vm specs (cpu/mem/disk speeds, utilization etc), and typical mail traffic statistics.
Who knows, maybe your trying to support X number of heavy users on too little ram, and adding more would be enough of a boost on it's own. Or you could have TB's of data and want to expand that by adding more on machine storage rather than mounted anyways. Or you already know that the box is underpowered cpu wise, so adding another vs migrating to just one more powerful. Hard drive IOPS, connections you can support, etc, etc.
Nginx Proxy for HTTP/IMAP/POP is up to you (among other things it helps if users can't remember another address like mail2.domain.com; though the web-client can do some basic redirect after auth, might still want it for thick-clients). A second MTA package or LDAP replica is likely overkill, unless this setup is extremely distributed across the globe where traffic can be an issue. But again all company specific, there's nothing stopping you from running mixes like:
S1: LDAP, MTA, Store, Logger, Proxy
S2: MTA, Store
Table of Contents :: Multi-Server Guide :: ZCS