Shared Mailboxes vs Distribution Lists: When to Use Each

If your business uses Microsoft 365 — and in 2026, the vast majority of UK SMEs do — you have almost certainly encountered the question of whether to set up a shared mailbox or a distribution list. Both allow multiple people to receive email sent to a single address, but they work in fundamentally different ways and serve distinctly different purposes. Choosing the wrong one leads to missed emails, duplicated responses, confused customers, and frustrated staff.

The problem is compounded by the fact that most businesses never formally decide which option to use. An IT administrator or office manager creates an address to solve an immediate need without considering the long-term implications. Six months later, the team is struggling with a workflow that was never designed for their actual requirements. Retrofitting the correct solution after the fact is always more disruptive than choosing correctly from the outset.

For UK businesses subject to regulatory obligations — whether under UK GDPR, FCA rules, or sector-specific compliance requirements — the choice carries additional weight. Shared mailboxes create auditable communication trails where every incoming and outgoing message is preserved in a single location. Distribution lists scatter emails across individual mailboxes, making it significantly harder to respond to subject access requests, regulatory audits, or internal investigations. Understanding these distinctions is not merely an IT decision; it is a business risk management decision that affects compliance posture, customer experience, and operational efficiency across the entire organisation.

The volume of email flowing through the average UK business continues to grow year on year. Research consistently shows that the typical UK knowledge worker sends and receives well over a hundred emails per day, and that figure rises considerably for customer-facing roles. When this volume of communication is routed through the wrong type of email group, the consequences compound quickly: missed customer enquiries, delayed invoice processing, overlooked supplier communications, and a general sense that email is something that happens to the team rather than something the team controls. The right choice of email structure — shared mailbox, distribution list, or Microsoft 365 Group — is the foundation upon which effective email management is built.

This guide explains exactly what shared mailboxes and distribution lists are, how they differ, when to use each, and how to set them up correctly in Microsoft 365. We also cover Microsoft 365 Groups and dynamic distribution lists, giving you the full picture of collaborative email options available to your business.

What Is a Shared Mailbox?

A shared mailbox is a dedicated mailbox in Microsoft 365 that multiple users can access, read, and send email from. It has its own email address — such as info@yourcompany.co.uk or accounts@yourcompany.co.uk — and its own inbox, sent items folder, and calendar. Team members are granted access to the shared mailbox, which then appears alongside their personal mailbox in Outlook.

The critical characteristic of a shared mailbox is that it is a collaborative workspace. When someone sends an email to the shared mailbox address, it arrives in the shared inbox where any authorised team member can see it, read it, and respond to it. Replies are sent from the shared mailbox address, so the external sender sees a consistent business identity rather than an individual person's email. Other team members can see that a reply has been sent, reducing the risk of duplicate responses.

Shared mailboxes in Microsoft 365 do not require a separate licence, making them a cost-effective solution. However, if the mailbox needs more than 50GB of storage, you must assign a licence to it.

How Shared Mailboxes Work in Practice

When an administrator grants a user access to a shared mailbox, Outlook automatically maps the shared mailbox and displays it in the user's folder pane beneath their personal mailbox. This auto-mapping feature means team members do not need to perform any manual configuration — the shared mailbox simply appears. On Outlook for the web, users can add the shared mailbox manually through their account settings, and on mobile devices, the shared mailbox can be added as a separate account or accessed through the Outlook mobile application.

There are two distinct permission levels for shared mailboxes: Full Access and Send As. Full Access allows a user to open the shared mailbox, read its contents, and manage its folders. Send As allows a user to send email that appears to come from the shared mailbox address. These permissions are independent — you can grant Full Access without Send As if you want someone to be able to read incoming mail but not respond from the shared address. Most organisations grant both permissions to team members who need to actively manage the mailbox.

A third permission option, Send on Behalf, allows users to send email that shows it was sent by the individual on behalf of the shared mailbox. This is useful when you want transparency about who specifically sent a response whilst still associating it with the shared address. For example, an email might appear as "John Smith on behalf of accounts@yourcompany.co.uk" in the recipient's inbox.

One practical consideration that many businesses overlook is shared mailbox auto-mapping behaviour. When auto-mapping is enabled, the shared mailbox appears in Outlook automatically for all users who have Full Access. For busy professionals who already manage a large number of folders, having multiple shared mailboxes auto-mapped can clutter their Outlook interface and slow down the application. Administrators can disable auto-mapping for specific users and instead have them manually add the shared mailbox, giving individuals more control over their Outlook layout. This is particularly relevant in organisations where staff members have access to several shared mailboxes but only actively work with one or two on a daily basis.

What Is a Distribution List?

A distribution list (also called a distribution group) is simply a way to send an email to multiple recipients using a single address. When someone sends an email to marketing@yourcompany.co.uk configured as a distribution list, Microsoft 365 delivers a copy of that email to each individual member's personal mailbox. There is no shared inbox — each person receives and manages the email independently in their own mailbox.

A distribution list is essentially a mailing list. It expands a single address into multiple individual deliveries. The recipients reply from their own email address, manage the email in their own inbox, and have no shared view of what others have received or responded to.

Managing Distribution List Membership

Distribution list membership can be managed in several ways. The simplest approach is for an administrator to manually add and remove members through the Exchange admin centre or Microsoft 365 admin centre. For larger organisations, dynamic distribution lists offer a more automated approach — membership is determined by filters based on user attributes such as department, office location, or job title. When a new employee joins the marketing department, for example, they are automatically added to the marketing distribution list without any manual intervention.

Distribution lists can also be configured with moderation, meaning that emails sent to the list must be approved by a designated moderator before being delivered to members. This is particularly useful for all-company distribution lists where you want to prevent accidental or inappropriate messages from being broadcast to the entire organisation. Moderation adds a layer of governance that can be valuable for larger businesses or those in regulated sectors where communications need to be carefully controlled.

It is worth noting that distribution lists can include external email addresses as members. This makes them useful for communicating with groups that include clients, partners, or suppliers alongside internal staff. However, including external addresses in distribution lists requires careful consideration of data protection obligations. Under UK GDPR, you must ensure that any personal data shared via the distribution list is being processed lawfully and that all recipients have a legitimate reason to receive the information being distributed. Regularly reviewing the membership of distribution lists that include external addresses is good practice for both security and compliance purposes.

Key Differences at a Glance

Feature	Shared Mailbox	Distribution List
Shared inbox	Yes — single inbox visible to all members	No — emails delivered to individual inboxes
Send as the group address	Yes — replies come from the shared address	No — replies come from the individual's address
Shared sent items	Yes — all members can see sent replies	No — sent items stay in each person's mailbox
Shared calendar	Yes — built-in shared calendar	No
Licence required	No (up to 50GB storage)	No
External senders	Can receive from external senders by default	May need configuration to accept external mail
Login required	No — accessed via delegation	No — delivered to personal inboxes

When to Use a Shared Mailbox

Shared mailboxes are the right choice whenever you need a team to collaboratively manage incoming email and present a unified identity to external contacts. Here are the most common use cases.

Customer service and support. An address like support@yourcompany.co.uk as a shared mailbox ensures every customer enquiry is visible to the whole support team. Anyone can pick up and respond to a query, and the customer always sees replies from the support address rather than an individual's email. Other team members can see when a query has been answered, avoiding embarrassing duplicate responses.

Accounts and finance. An accounts@yourcompany.co.uk shared mailbox allows your finance team to collaboratively manage invoices, payment queries, and supplier correspondence. The shared sent items folder creates an audit trail of all outgoing communication.

General enquiries. An info@ or hello@ shared mailbox is ideal for managing general business enquiries that could be handled by multiple team members.

Project-specific communication. For significant projects involving multiple team members, a project-specific shared mailbox keeps all correspondence in one place and accessible to everyone involved.

When to Use a Distribution List

Distribution lists are the right choice when you want to broadcast information to a group of people and do not need collaborative inbox management. Common use cases include the following.

Company-wide announcements. An allstaff@yourcompany.co.uk distribution list delivers announcements, policy updates, and company news to every employee. There is no need for a shared inbox because the communication is one-way.

Department broadcasts. A marketing-team@yourcompany.co.uk distribution list allows anyone in the business to send information to the entire marketing department without needing to know every individual's email address.

External mailing lists. Distribution lists can include external email addresses, making them useful for sending regular updates to clients, partners, or suppliers.

What About Microsoft 365 Groups?

Microsoft 365 Groups are a newer collaboration option that blurs the line between shared mailboxes and distribution lists. A Microsoft 365 Group creates a shared mailbox, a shared calendar, a SharePoint document library, a OneNote notebook, and a Planner board — all connected under a single group identity.

Groups are powerful for teams that need more than just shared email. If your team needs to share files, manage tasks, and communicate via email from a single identity, a Microsoft 365 Group may be more appropriate than a standalone shared mailbox. However, Groups come with more complexity and can create sprawl if not managed carefully.

Governance and Lifecycle Management for Groups

One of the significant challenges with Microsoft 365 Groups is governance. Because Groups are easy to create — any user can create one by default — organisations can quickly end up with dozens or even hundreds of Groups, many of which are inactive or redundant. Microsoft provides tools for managing this sprawl, including Group expiration policies that automatically delete Groups after a period of inactivity, naming policies that enforce consistent naming conventions, and sensitivity labels that control who can create Groups and what features they include.

For UK businesses evaluating whether to use a Microsoft 365 Group or a shared mailbox, the decision often comes down to scope. If the requirement is purely email-based collaboration — managing a shared inbox, sending replies from a common address, and maintaining a shared calendar — a shared mailbox is simpler, easier to manage, and perfectly sufficient. If the requirement extends to document collaboration, task management, and team communication beyond email, a Microsoft 365 Group provides a more comprehensive solution. The key is to avoid using Groups for simple email scenarios where a shared mailbox would suffice, as the additional features add complexity and administrative overhead that may not be justified.

It is also worth considering that every Microsoft 365 Group creates a shared mailbox as part of its resources. However, this Group mailbox behaves differently from a standalone shared mailbox. Group mailboxes have a conversation-style view in Outlook rather than a traditional inbox view, which some users find less intuitive for managing incoming enquiries. If the email experience is the primary requirement, a standalone shared mailbox typically provides a better and more familiar user experience for most teams.

Dynamic distribution lists deserve special mention in this context. Unlike standard distribution lists with manually managed membership, dynamic distribution lists automatically include or exclude members based on directory attributes. For example, you could create a dynamic distribution list that automatically includes every employee in the London office, or every member of the finance department. When staff join or leave the relevant group, the distribution list updates automatically. This reduces administrative burden significantly for larger organisations where team composition changes frequently.

Common Mistakes and How to Avoid Them

Using a distribution list when you need a shared mailbox. This is the most common mistake. A distribution list for support@ means customer emails land in multiple individual inboxes with no shared visibility. Multiple people reply to the same email independently, and the customer receives conflicting responses. Use a shared mailbox for any address that requires collaborative response management.

Not configuring external sending permissions. By default, distribution lists in Microsoft 365 only accept email from internal senders. If customers need to email a distribution list address, you must explicitly enable external delivery in the Exchange admin centre.

Forgetting to manage membership. When staff leave the business, their access to shared mailboxes should be revoked and their membership of distribution lists removed. Failing to do this creates security risks — particularly if the former employee's personal mailbox is not immediately disabled, as they could continue receiving emails from distribution lists.

Exceeding shared mailbox storage limits. The free 50GB storage limit on shared mailboxes sounds generous, but a busy shared mailbox that receives attachments can fill up surprisingly quickly. Implement a retention policy to automatically archive or delete old emails, or assign a licence to increase the storage to 100GB.

Setting Up a Shared Mailbox in Microsoft 365

Creating a shared mailbox is straightforward for anyone with Microsoft 365 admin access. Navigate to the Microsoft 365 admin centre, select Teams and Groups, then Shared Mailboxes, and click Add a Shared Mailbox. Enter the display name and email address, add the members who should have access, and configure permissions for Send As and Send on Behalf. Members will see the shared mailbox appear in their Outlook client automatically, though it may take up to an hour to propagate.

For UK businesses handling personal data, remember that shared mailboxes are subject to UK GDPR. Ensure access is restricted to authorised personnel and that retention policies are configured appropriately. If the shared mailbox receives subject access requests or data-related enquiries, establish a clear process for handling these within the required timescales.

Choosing the Right Option for Your Business

The choice between a shared mailbox and a distribution list should be driven by the purpose of the email address. If the address needs collaborative management with a shared view of incoming and outgoing email, use a shared mailbox. If the address simply needs to deliver email to multiple people for informational purposes, use a distribution list. If you need broader collaboration including files and tasks, consider a Microsoft 365 Group.

Most businesses end up using a combination of all three. A typical UK SME might have shared mailboxes for info@, support@, and accounts@; distribution lists for allstaff@ and management@; and Microsoft 365 Groups for project teams and departments. The key is choosing the right tool for each specific purpose.