Your clients email you to ask things a screen could answer: where the job stands, or for another copy of something you already sent. We build a portal on your own domain that shows each client their whole job, so most of those emails stop.
Yours is built from scratch, so the list is whatever your business needs. If your clients keep asking for something that isn't on it, we add it.
A "just checking in" email pulls somebody off real work to answer something the system already knows. In the portal every job shows where it stands and what happens next, updated the moment your team updates it, so clients look instead of writing.
The signed contract is in a February email thread, and the version your client has open is two revisions old. Every document in the portal has one copy, the current one, so "can you resend that" stops arriving.
An invoice sent by email waits for somebody to dig it out. One in the portal sits next to everything else your client checks, has a card button on it, and sends its own reminder when it falls due.