Shared Mailbox vs User Mailbox: When Should a Business Use Each?

Use a user mailbox for a person’s working email and a shared mailbox for an address that authorised colleagues manage together. A sales@ inbox normally belongs to a role or team; an employee’s day-to-day inbox belongs to that individual. Both can support delegated access, but the sign-in, ownership and licensing decisions differ.

For a UK business, the useful question is not simply which mailbox costs less. It is who needs to do the work, what customers should see and what happens when a colleague changes role or leaves. A cheap-looking setup becomes awkward if everybody shares one login or nobody can find the last reply.

This guide covers Microsoft 365 business email in Exchange Online. It explains the choice, with sales-team and leaver examples. If the mailbox already exists and you need to open it, use our step-by-step guide to adding a shared mailbox in Outlook.

Technical and licensing guidance checked against Microsoft documentation on 8 November 2026. Examples are illustrative. Confirm the licences, policies and contractual terms that apply to your organisation before making changes.

What is a shared mailbox?

A shared mailbox is a common inbox, with a calendar, that authorised users access through their own work accounts. It suits addresses such as sales@, accounts@ or reception@ when more than one person needs to read and respond to the same correspondence.

The mailbox is separate from each colleague’s own inbox. It can keep a customer conversation available to the team when the person who first replied is on leave. Microsoft describes these uses in its overview of shared mailboxes and calendars.

It is not a shared username and password. Keep direct sign-in blocked for the shared mailbox account and grant access to named people instead. Nor does creating an address called sales@ automatically make it a shared mailbox: IT should check the actual Exchange mailbox type.

Shared mailbox vs user mailbox at a glance

Decision	User Mailbox	Shared Mailbox
Main Purpose	A Person’s Working Email and Calendar	A Common Address Managed by Authorised Colleagues
Normal Access	The Person Signs In With Their Own Identity	Delegates Sign In With Their Own Identities and Open the Shared Mailbox
Team Cover	Can Be Arranged Through Delegation	A Core Reason to Use It
Sending Identity	Usually the Individual; Delegated Sending Is Possible	Shared Address or Delegate on Behalf of It, Depending on Permission
Licensing	Needs the Appropriate Exchange Online Entitlement	May Not Need Its Own Licence Within the Standard Conditions; Accessing Users Still Need Licensed Mailboxes
Typical Example	A Salesperson’s Individual Correspondence	sales@ for a Team’s Common Enquiries
Main Governance Question	Who Owns This Person’s Work and Approved Cover?	Who Owns the Inbox, Its Membership and Its Response Process?

Delegation is not exclusive to shared mailboxes. For example, a director can keep a user mailbox while an assistant receives approved access. The need for cover alone does not require converting someone’s personal working mailbox. Microsoft documents Full Access and delegated sending for Exchange Online recipients.

Use a shared mailbox for a team address such as sales@

Imagine a three-person sales team. Customers should be able to email one address even when the person handling their account is away. A shared sales@ mailbox can give the authorised team one place to receive enquiries and retain replies.

Before launching it, make four decisions:

1. Name an owner. Someone must approve membership, review access and deal with unanswered enquiries.
2. Agree the sender. Should replies come from sales@, or show an individual acting on its behalf?
3. Make the history usable. Check that colleagues can see sent replies, not just incoming messages.
4. Define a handover method. Agree how people claim an enquiry, record progress and arrange cover.

These are operating choices, not features that a mailbox type decides for you. A simple team might agree categories and a clear handover note. A busy operation may need a CRM or ticketing system with assignment, deadlines and reporting. If staff often ask “Has anyone answered this?”, investigate the workflow before adding more folders.

The recipient-facing address can stay consistent while team membership changes. When someone leaves, remove that person’s delegated access rather than passing their credentials to a replacement. Review our Microsoft 365 offboarding checklist for the wider departure process.

Keep a user mailbox for an employee’s day-to-day work

An employee who sends their own correspondence, manages their calendar and signs in to Microsoft 365 needs an appropriately licensed identity and mailbox. A shared team address can sit alongside that mailbox; it does not replace the employee’s entitlement to use the service.

For example, a salesperson can keep their individual mailbox for one-to-one client work while also accessing sales@ for incoming team enquiries. This makes the distinction visible: one address identifies the person, the other identifies a business function.

If an assistant needs access to a director’s inbox, start with the approved delegation requirement. Define what they can read, whether they can send and how that sending should appear. Do not convert an active employee’s mailbox simply because two people need to see some of its contents.

Also check dependencies before changing any mailbox type. Ask whether applications, workflows or devices use that identity. A process that expects to sign in as a user needs a supported authentication design; relabelling the mailbox does not resolve that dependency.

Understand permissions and accountability

There are two distinct questions: who can open the mailbox, and who can send from it?

• Full Access permits working with mailbox contents but does not itself grant sending rights.
• Send As presents the mailbox as the sender.
• Send on Behalf presents the delegate acting on behalf of the mailbox.

Check the actual assignment rather than inferring it from what Outlook displays. Full Access is substantial access, so grant it only where the business need justifies it. Restrict particularly sensitive correspondence to the right group of people.

A shared sender does not remove the need for an audit trail

Customers seeing sales@ does not mean the business should lose track of who acted. Named delegate accounts give administrators a basis for investigating activity. Microsoft provides shared mailbox audit investigation procedures for actions such as sending, deletion and rule changes.

Audit evidence depends on the configured logging, available retention, permissions and licences. Ask IT what can actually be investigated and for how long. Do not assume every read or every historical action is recorded indefinitely.

An audit log and a team work queue serve different purposes. A log may help investigate an action later; it does not tell a colleague which unanswered enquiry they should handle next. Keep a clear response process as well.

Check the licensing conditions before calling it free

Microsoft allows a shared mailbox to hold up to 50 GB without its own licence under the standard conditions. The people accessing it still need their own licensed Exchange Online mailboxes. A shared address is therefore not a way to supply unlicensed staff with business email.

Capacity and additional features can change the requirement. Microsoft’s current guidance specifies Exchange Online Plan 2 for a 100 GB shared mailbox; archiving, litigation hold, and advanced security or compliance capabilities require their own entitlement checks. See the current shared mailbox licensing conditions.

Use a requirement checklist before removing an assigned licence:

Check	Question to Resolve
Primary Mailbox Storage	Is Usage Within the Unlicensed Limit, With Room to Grow?
Archive	Is an Archive Enabled, and What Entitlement Does It Need?
Preservation	Are Holds, Retention or eDiscovery Requirements in Place?
Security	Which Protection Features Apply, and Who Needs Licensing?
Accessing Staff	Does Each Delegate Have the Required Licensed Mailbox?
Subscription	Can the Paid Seat Quantity Actually Be Reduced Under the Agreement?

Ask the licensing administrator to record the relevant plans and service features. “It is now shared” is not enough evidence to remove every licence attached to an account.

Releasing an assigned licence, reusing a seat and reducing a subscription charge are separate events. If the subscription quantity cannot be reduced immediately, a conversion may free a seat for another employee without changing the current bill. TechVertu’s software licensing services cover the wider licensing review.

Handle a leaver’s mailbox as an approved handover

Suppose a salesperson leaves and their manager needs temporary access to outstanding customer correspondence. Converting the user mailbox to shared can be appropriate, but it is one part of the departure process.

First establish the business purpose, approved recipients, required information and review date. Access to an entire former employee’s inbox may be broader than the handover needs. Involve the responsible HR and data owners, especially where the mailbox may contain private or sensitive material.

Microsoft says conversion retains existing email and calendar information. It also says to keep the associated account because it anchors the shared mailbox. Conversion alone does not secure the former employee’s access. See Microsoft’s conversion prerequisites.

Use this sequence for the decision and handover, with IT carrying out the technical changes:

1. Approve the scope. Record the purpose, authorised delegates and access review date.
2. Secure the identity. Follow the departure process for blocking sign-in, revoking sessions and other connected access.
3. Preserve what is required. Check holds, retention, storage and archive requirements before changing licensing.
4. Convert and verify if approved. Keep the account anchor, grant the agreed access and test the needed mailbox functions.
5. Review licensing and closure separately. Confirm entitlements, paid-seat terms and the eventual retention or deletion decision.

For the complete procedure, use our employee offboarding checklist. Avoid copying a whole former employee’s inbox into a new starter’s mailbox just to make the handover convenient.

Choose another tool when the requirement is different

A shared mailbox is useful for a common inbox, but it is not the answer to every shared-address request.

• Another address for one existing inbox: Ask whether an alias would meet the need.
• Distributing messages to several people: Assess a distribution group rather than assuming you need one shared work queue.
• Project collaboration: Compare a Microsoft 365 group and its associated collaboration features.
• Assigning work, tracking response times or reporting on a service desk: Assess a CRM or ticketing system.

Keep the requirement specific. “Three people must read every enquiry and one must own the response” is more useful than “We need another email address.” Microsoft’s comparison of Microsoft 365 groups can help distinguish the available group types.

Record the decision before you change anything

For each address under review, record its purpose, accountable owner, users, intended sender, storage, retention requirements and next review date. Add any application dependency and the licence decision.

Then test the outcome with harmless content. Can the right person open the mailbox? Does the recipient see the intended sender? Can another authorised colleague find the reply? Is the former employee’s sign-in blocked where applicable? These checks reveal more than simply confirming that an address exists.

Once you have chosen a shared mailbox, follow the separate Outlook setup guide for new, classic, web and Mac. Keep the choice of mailbox type and the instructions for opening it as two distinct tasks.

Frequently asked questions