Not front to back. Jump in wherever you are stuck — the four stages are dependencies, not difficulty levels. A just want it working locally · B worried about losing an account, and where the money goes (the spine is here) · C want it running while you are away · D need it up around the clock.
Get it changing your code · Install, permissions, config layers
Accounts, quota, relays · So one dead account does not end the whole thing
From "I type a line" to "it runs itself" · Schedules, hooks, always-on agents, messaging
From local to around the clock · When a machine is really needed, and surviving it