Why not just share a login
Plenty of small offices still run info@ as an ordinary user account and pass the password around the team. It works until someone leaves and nobody changes the password, or until multi-factor sign-in is switched on and the code goes to one person's phone. It also means every action looks like it came from the same person, so there is no way to tell who deleted a supplier's email or replied rudely to a customer.
A shared mailbox removes those problems. Nobody signs into it directly; staff open it from their own account, protected by their own password and sign-in checks. Access is given and removed per person, and the audit trail shows who did what. On most business plans a shared mailbox also needs no licence of its own while it stays under its size threshold, so it often saves money as well as risk.
Creating the mailbox
In the Microsoft 365 admin centre, go to Teams and groups, then Shared mailboxes, and add a new one with a display name and address. The display name is what customers see in their inbox, so choose something like Accounts - Harbour Joinery rather than just accounts. Then add the members who need access. Within an hour or so, Outlook on their computers picks it up and shows it below their own mailbox.
If you are converting an existing user mailbox such as info@ into a shared one, the admin centre has a convert option that keeps all the existing email. Remove the licence only after conversion and after checking the mailbox is under the free size limit, otherwise mail may stop arriving.
Read access, Send As and Send on Behalf
Access has three parts. Full access lets someone open the mailbox and read, file and delete mail. Send As lets them send an email that appears to come from the shared address alone. Send on Behalf shows the recipient that a named person sent it on behalf of the shared address. For a customer-facing inbox, Send As usually looks cleaner; for an executive assistant replying for a director, Send on Behalf can be more honest. Grant only what each person needs. A junior who triages the inbox may need read access but not the ability to send. A part-time bookkeeper may need Send As for accounts@ but no access to the general enquiries mailbox.
Sent items and replying from the right address
A common complaint is that replies sent from the shared mailbox land in the sender's own Sent Items instead of the shared one, so colleagues cannot see what was said. Newer versions of Outlook and Microsoft 365 handle this better, and an administrator can set the mailbox to keep a copy of sent items in its own Sent folder. Make sure that setting is on before the team starts using it.
The other mistake is replying from a personal address by accident. In Outlook, show the From field on new messages and pick the shared address. When replying to an email that arrived in the shared mailbox, Outlook usually picks the right address automatically, but it is worth checking until it becomes habit.
Working as a team in one inbox
Once three or four people work out of the same inbox, you need a simple system or emails get answered twice or not at all. Categories are the easiest tool: colour-code emails by the person handling them, or by status such as waiting on supplier. Flagging and moving finished items into a Done folder keeps the Inbox showing only open work.
Agree who covers the inbox on which days, especially over lunch and holidays. If volume grows to hundreds of emails a day, or you need response time tracking, a help desk or ticketing tool connected to the mailbox will serve you better. A shared mailbox is excellent up to a point, but it was not designed as a full case management system.
Mobile access and housekeeping
Shared mailboxes can be added to the Outlook app on phones, which helps for a bookings inbox that needs checking after hours. The setup is slightly different from desktop Outlook, so walk staff through it once. Keep the shared mailbox tidy with the same retention and archiving approach you use elsewhere, and give it a named owner who reviews the access list each quarter. When someone leaves, removing them from the member list is part of the offboarding checklist. Because nobody ever had the mailbox password, there is nothing to change, which is the whole point of using a shared mailbox in the first place.
In short
- Shared mailboxes replace shared passwords with per-person access.
- Pick Full Access, Send As and Send on Behalf per person, not by default.
- Turn on saving sent items in the shared mailbox before the team starts.
- Use categories and a Done folder so nothing gets answered twice.