What a shared mailbox is

A shared mailbox is an email address that several people can read and send from, without anyone needing its password. Typical examples are info@, enquiries@, accounts@, bookings@ and support@.

Each person who needs it is given access, and the shared mailbox appears in their own Outlook next to their personal mailbox. When someone replies, the customer sees the shared address, not the member of staff. When that person leaves, you remove their access and the shared mailbox carries on with all its history.

How it saves licence costs

This is the part many small businesses miss. In Microsoft 365, a shared mailbox does not need its own licence as long as it stays under 50 GB and does not need extras such as an online archive or litigation hold.

The common alternative is to create info@ as a normal user, buy it a licence and share the password around the office. That costs a licence every month for each address, and a shared password is a security problem: it cannot have proper multi-factor authentication, and you cannot tell who sent what.

  • Each address you move from a licensed user to a shared mailbox is one less monthly licence.
  • When someone leaves, you can convert their mailbox to a shared mailbox so the emails are kept and colleagues can still reach them, then remove the licence.
  • Every person who opens a shared mailbox still needs their own licensed account. The saving is on the shared address itself, not on the people using it.

How to create a shared mailbox

You need to be a Microsoft 365 administrator.

  1. Sign in to the Microsoft 365 admin centre at admin.microsoft.com.
  2. Go to Teams & groups, then Shared mailboxes.
  3. Click Add a shared mailbox. Give it a display name, such as "Acme Enquiries", and the email address, such as enquiries@yourbusiness.co.uk.
  4. Click Save changes. It can take a few minutes to appear.
  5. Under the new mailbox, choose Add members and select the people who should have access.

Microsoft blocks direct sign-in to new shared mailboxes. Leave it that way. People should always open it through their own account.

Send As or Send on Behalf

There are two ways staff can send from a shared mailbox, and they look different to the customer:

  • Send As: the email appears to come from the shared address only, for example "Acme Enquiries". This is usually what a business wants.
  • Send on Behalf: the email shows "Jane Smith on behalf of Acme Enquiries".

In the admin centre, open the shared mailbox and set these under Manage mailbox permissions. Give staff Read and manage, plus Send As if they need to reply from it.

Opening it in Outlook

Classic Outlook for Windows: once someone has Read and manage access, the shared mailbox normally appears by itself in the folder list after Outlook is restarted. This can take up to an hour.

New Outlook and Outlook on the web: right-click Shared with me or the folder list and choose Add shared folder or mailbox, then type the shared address.

Phones: the Outlook mobile app can add a shared mailbox under Add account, then Add a shared mailbox, once the person has access.

To send from it, click From in a new email and pick the shared address. If the From box is not showing, turn it on under the Options tab when writing an email.

Replies sent from a shared mailbox in classic Outlook are saved in the sender's own Sent Items by default. An administrator can change this so sent emails are also copied to the shared mailbox's Sent Items, which makes it much easier to see who has replied to what.

Converting a leaver's mailbox

When someone leaves, converting their mailbox keeps their emails and lets colleagues pick up conversations, without paying for a licence:

  1. Reset the leaver's password and sign them out of all sessions.
  2. In Users, Active users, select them, open the Mail tab and choose Convert to shared mailbox.
  3. Give the right colleague access.
  4. Once it shows as shared, remove the licence. Check it is under 50 GB first.

Shared mailbox or Microsoft 365 group?

A Microsoft 365 group also has an email address, plus a shared calendar, files and a Team. It suits a project or department. A shared mailbox suits an address that customers write to and that a few people need to answer. For info@ and accounts@, a shared mailbox is the simpler choice.

When to ask for help

If your business has several addresses set up as paid users with shared passwords, sorting them out usually saves money every month and closes a security gap at the same time. RoamTech does this remotely for small businesses anywhere in the UK, as part of Business IT Support or as a one-off job. See setting up Microsoft 365 for the wider picture.