Almost every email provider prices by headcount, so almost every business organizes its email by headcount too. You get an address per employee, and everything else — projects, properties, clients, job numbers — gets crammed into those addresses and sorted out later with folders and filters and memory.
A mailbox per project inverts that. The address belongs to the work rather than the worker, which sounds like a small administrative distinction until the person who owned the thread leaves, or two people need the same history, or a client asks what was agreed in March. This page is about when that pattern is worth adopting, what it costs when mailboxes aren't priced per seat, and where it goes wrong.
The Shape of a Mailbox Per Project
The shape is simple. Instead of routing everything through people, you create an address for the unit of work itself and let the relevant humans read it.
The same pattern wears different clothes depending on the trade. A construction firm creates one per job number. A letting agency creates one per property. An agency creates one per client and keeps it through three account managers. A manufacturer creates one per production run. In every case the logic is identical: correspondence attaches to the thing it's about, and stays attached when staff change.
What makes a mailbox per project practical rather than theoretical is whether creating the two-hundredth address costs anything. Under per-seat pricing it costs the same as the first, which is why nobody does this on Google Workspace or Microsoft 365. At the $7 Business Starter seat on Google's own pricing page, five hundred project mailboxes is $42,000 a year, and the idea dies in the budget meeting.
The Arithmetic That Makes It Possible
Our plans cap counts by tier rather than charging per mailbox. Pro allows 300 mailboxes per domain across 100 domains with 50 GB of pooled storage; Agency allows 1,000 per domain across 1,000 domains with 200 GB, at $29 a month or $279 a year.
So five hundred project mailboxes on Agency is $279 a year rather than $42,000. The constraint moves from money to storage: 200 GB across 500 mailboxes is roughly 410 MB each, which is generous for correspondence and tight if every thread carries drawings or photographs. If that ceiling is the binding one, the Drive add-on starts at $3.20 a month and lifts it without changing the mailbox arithmetic at all.
That's the actual trade. A mailbox per project is cheap in license terms and costs you storage planning instead, which is a much easier problem to manage than a per-seat bill that grows every time you win work.
Why This Beats Folders and Filters
The obvious objection is that folders already solve this. They don't, quite, and the reasons are worth being specific about.
Folders live inside one person's mailbox. When that person is away, the history is away too, unless someone has set up delegation that nobody tested. A project address is reachable by everyone who should reach it, by design rather than by exception.
Filters run on the recipient, not the subject. Mail addressed to a person and merely about a project has to be classified by rules that break the moment a client replies with a changed subject line or a new address. Mail addressed to the project needs no classification.
Handover becomes a membership change. When staff turn over — and in agencies and lettings they turn over constantly — a mailbox per project means the incoming person gets access to the complete history immediately. Nothing is forwarded, nothing is exported, nothing is lost in a PST file on a laptop that went back to IT.
Filters are still useful, of course, and they arrive on Pro rather than Starter, which catches people out. The point is that they solve a different problem than a mailbox per project does.
Making It Work in Practice
A few details separate the setups that survive from the ones abandoned after a quarter.
Name them predictably. Whatever the scheme, make it derivable — job numbers, property references, client codes. If somebody has to look up the address, the pattern is already failing.
Create them in bulk. Making two hundred mailboxes by hand is nobody's afternoon. Bulk creation and setup invites mean addresses can be provisioned in one operation, with the people who need them setting their own passwords rather than having credentials handed around, which is covered in creating mailboxes in bulk.
Decide who reads what before you start. A mailbox per project is only useful if the right people are in it. Shared mailboxes with real membership are the mechanism, and they behave differently from forwarding — the detail is in how shared mailboxes work.
Plan the ending. Projects finish. Decide up front whether a finished project's mailbox is archived, left dormant or deleted, because the failure mode of this pattern is accumulation.
When a Mailbox Per Project Is the Wrong Idea
It suits some work badly, and it's better to know that before provisioning three hundred addresses.
If your projects are numerous and tiny — dozens a week, each generating two emails — the overhead of creating and retiring addresses exceeds any benefit, and a shared inbox with sensible filters is the better answer. If correspondence genuinely is personal, as in most sales relationships, the address should follow the person because that's what the counterparty expects. And if nobody ever needs to see anyone else's threads, you're solving a problem you don't have.
The pattern earns its keep where work outlives the worker, where more than one person needs the same history, and where somebody will eventually ask what was agreed and when. That describes agencies, lettings, construction, professional services and manufacturing rather well, and describes a two-person consultancy hardly at all.
Who Reads What
A mailbox per project only pays off if access is arranged deliberately, and there are three ways to do it with quite different consequences.
A shared mailbox with membership is the usual right answer. Several people open the same mailbox, everyone sees the full history including replies sent by colleagues, and adding or removing a person is a membership change rather than a credential handover. Sent mail lives with the project rather than scattered across individual Sent folders, which is the detail that makes handover actually work.
Forwarding into personal mailboxes looks simpler and quietly loses you the benefit. Each person gets a copy, replies leave from personal addresses, and the project has no record of what was said — you've rebuilt the problem with extra steps.
A mailbox with shared credentials is the arrangement to avoid outright. Nobody can tell who did what, offboarding means changing a password everyone knows, and two-factor becomes impossible to manage sensibly.
Shared mailboxes are available from Starter, at five per domain, rising to fifteen on Pro and thirty on Agency. That per-domain ceiling is the number to check against your project count before committing to the pattern.
Two Years In
The pattern's real test is whether it degrades, and the honest answer is that it does unless one decision is made early.
Finished projects accumulate. After two years you have hundreds of mailboxes, most of them dormant, all of them consuming a little storage and cluttering every list. The teams that stay happy with a mailbox per project are the ones that decided at the start what happens when a project closes.
The workable options are archiving the mail and deleting the mailbox, which reclaims the slot and keeps the history; leaving it dormant, which costs a slot but keeps everything reachable; or converting it back to a regular mailbox nobody monitors. Which you choose matters far less than choosing at all.
The related decision is what happens to the address itself. A job number's address that stops accepting mail will bounce late-arriving correspondence — an invoice, a warranty claim, a query from a supplier who kept the old address. Keeping the address alive with a catch-all destination while retiring the mailbox handles that case and costs nothing.
Starting Small
You don't have to commit the whole business. Take the projects that have caused the most confusion in the last year — the ones where someone had to go digging through an ex-colleague's mailbox — and give those an address each.
If it holds for a quarter, widen it. If it doesn't, you've spent nothing but a few minutes, because the mailboxes weren't costing you anything per seat in the first place. That's the underlying point: a mailbox per project stops being an expensive reorganization and becomes a cheap experiment the moment mailboxes aren't billed by the head.
