Shared Mailboxes, Aliases and Groups in Microsoft 365

A business address such as accounts@example.com can mean several different things. It might deliver to one employee, put a copy in several inboxes, or open a mailbox that a team works in together. The address itself does not tell you which arrangement you have.

That distinction matters when someone is away, a customer needs a reply, or an employee leaves. The useful question is where the conversation should live and who needs to act on it. Microsoft 365 offers several ways to meet those needs.

Four ways to use a business email address

Microsoft's comparison of group types describes the underlying purposes. Distribution groups deliver to recipients; Microsoft 365 groups support collaboration and can connect to SharePoint, Planner and Teams. Those connected resources make a group a broader decision than an extra email address.

An alias gives an existing mailbox another address

An alias is useful when one person needs to receive mail under another spelling, a former surname or a second business address. Mail sent to either address reaches the same mailbox. It does not create a second place to organize messages, a separate calendar or another person's access.

For example, an owner might receive both charles@example.com and cstaal@example.com in one inbox. That works well if both addresses represent the same person. It is less suitable when a growing accounts team needs to share a continuing role.

Microsoft does not charge an additional alias license. Sending from an alias depends on the organization's settings and the Outlook client in use, so the appearance of outgoing replies should be checked rather than assumed. See Microsoft's email alias guidance.

A shared mailbox keeps a role's correspondence together

A shared mailbox can give two receptionists access to the same incoming appointments and supplier messages. Each person signs in through their own licensed account and opens the mailbox they have permission to use. A shared password should not become the way the team accesses it.

Microsoft says to keep direct sign-in blocked on the account associated with a shared mailbox. Delegates need an Exchange Online license. The shared mailbox itself can hold up to 50 GB without its own license; larger storage, archiving, holds and some advanced protection or compliance features can introduce licensing requirements. Outside users cannot simply be added as shared-mailbox delegates. These limits are detailed in Microsoft's shared mailbox reference.

For a business owner, the benefit is continuity. The address belongs to the function, and the people responsible for that function can change. Decide who owns the mailbox, who approves access and who covers it during absences. Adding everyone because they might occasionally help can expose far more correspondence than the business intended.

Reading a mailbox and sending from it are separate permissions

Someone may be able to open a shared mailbox without being able to send from its address. Full Access allows mailbox access. Send As lets the recipient see the shared identity as the sender. Send on behalf identifies that a person is sending on behalf of that identity. They serve different purposes and should be requested deliberately. Microsoft's mailbox permissions guide explains the distinctions.

Consider invoices. A business might want replies to come from Accounts so customers have one consistent contact. For correspondence where the responsible individual should be visible, sending on behalf may be more appropriate. Agree on the desired result before treating an unexpected From address as an Outlook fault.

A shared inbox does not automatically provide a complete reply history

One of the easiest problems to miss is where outgoing messages are saved. A colleague may read an incoming message in Accounts, reply successfully, and leave the next person unable to see that reply in Accounts' Sent Items.

Microsoft provides settings to retain copies of messages sent as, or on behalf of, the shared mailbox. By default, sent messages can be kept in the sender's own Sent Items instead. The shared mailbox settings documentation covers this behavior. A real reply test is more useful than confirming that the mailbox appears in Outlook.

Even with a common reply history, a mailbox does not necessarily show who has taken responsibility for each request. If several people regularly duplicate replies or leave messages unanswered, the business may need an agreed triage routine or a ticketing system with assignment and status. Changing the email object alone will not settle those working arrangements.

Example: sharing the accounts inbox

Imagine a small company where the office manager currently receives Accounts mail as an alias. A second employee starts helping with invoicing, and the manager needs vacation coverage without handing over a personal inbox.

One person handles itAlias → that person's mailbox

Several people need a copyDistribution group → recipients' inboxes

A team handles a continuing roleShared mailbox → shared correspondence

A shared Accounts mailbox may fit the third arrangement. Before changing anything, the company should decide which existing messages belong to the business role and which are private to the manager. The address needs a planned handover; creating a new mailbox does not move the old messages automatically.

The handover should also settle who watches new mail, where replies are saved, and how work is covered. A short acceptance exercise can follow an incoming supplier invoice through receipt, reply and a second colleague's review. Include the phone app if staff actually use it.

When a distribution group or Microsoft 365 group fits better

A distribution group suits a message that several people need to receive, such as a notice to site supervisors. The fact that everyone received a copy does not show that anyone accepted responsibility for answering it. For messages requiring one accountable response, that distinction deserves attention.

A Microsoft 365 group suits a team whose collaboration extends to files, a shared calendar and other connected tools. Before inviting an outside collaborator, examine the group's resources and guest settings as a whole. A narrow email need should not accidentally become a much wider sharing decision. Our Microsoft 365 ownership worksheet helps record who approves those changes.

What changes when an employee leaves?

Microsoft supports converting an existing user mailbox to a shared mailbox while retaining its email and calendar. The associated account must remain because it anchors the mailbox, and the conversion is separate from preventing the former employee from signing in. Review storage, archive and hold requirements before removing a license. See Microsoft's conversion guidance.

A business should also choose who may read the old correspondence, for how long, and how new senders will be directed to the right person. An automatic reply, a role address and controlled access may each solve a different part of the handover. Avoid making a former employee's identity the permanent public face of a department.

For the broader setup and access process, use the employee onboarding reference. For the license capabilities behind these arrangements, see the Microsoft 365 Business plan comparison.