Microsoft 365 Group vs Shared Mailbox vs Distribution List: What to Use When in Outlook

Short answer: use a distribution list to broadcast one email to many people, a shared mailbox when a team needs to read and reply from one address like support@ or info@, and a Microsoft 365 Group when that same team also wants a shared calendar, files, and Planner alongside the inbox. All three let several people work with one role-based address in Outlook, but they solve different problems. This guide compares them side by side, then shows how to add ownership and history on top once your team outgrows the basics.

Quick comparison

What is a distribution list?

A distribution list (also called a distribution group) is simply a forwarding address. When someone emails the list, Microsoft 365 delivers a copy to each member's own mailbox. There is no shared inbox, no shared history, and no way to reply as the list — each member answers from their own address. Distribution lists are ideal for one-way communication such as announcements or "all-staff@" notices, and they need no license. They fall apart as a team inbox, because two people can answer the same message with no idea the other already did.

What is a shared mailbox?

A shared mailbox is a single mailbox that multiple people open and work from. It has its own inbox, its own Sent Items, and its own calendar, and everyone with access sees exactly the same messages. Team members can reply using the shared address, so a customer who writes to support@ gets an answer from support@. A shared mailbox is free up to 50 GB of storage; beyond that, or to enable an online archive or litigation hold, each shared mailbox needs an Exchange Online Plan 2 license. This is the most common choice for a small team working a role-based address like support@, info@, or finance@.

For a deeper look at running one well, see our guide to Outlook shared mailbox best practices and limitations.

A shared mailbox shows everyone the same inbox, but it can't tell you who is handling which email. SBX adds an assignee, an open/closed status, and a full history to every message, so the shared inbox becomes a set of clear, owned tasks instead of a pile everyone has to re-read.

What is a Microsoft 365 Group?

A Microsoft 365 Group is Microsoft's modern successor to the distribution list. Creating a group provisions a shared mailbox and calendar plus a SharePoint site, a Planner, and — optionally — a Team, all tied to one membership list. Members can follow the group so its email also lands in their own inbox, and because each person keeps their own Outlook profile, user-specific rules, categories, and folders are possible. The trade-off is that the group mailbox has fewer built-in email-collaboration controls than a shared mailbox, and it is often chosen because the team already needs a group for files or Teams anyway.

Read more in our guide to Microsoft 365 Groups best practices and limitations.

SBX works on top of a Microsoft 365 Group without changing the address or migrating anything. It restores team-wide shared categories and adds assignment, status, internal notes, and a full activity history — the email-workflow layer a group mailbox lacks — while your files and calendar stay exactly where they are.

Which one should you use?

Choose based on what the team actually needs to do with the address.

Use a distribution list when

You only need to send one email to many people, and no one needs to reply as the address or see a shared history. Announcements, newsletters, and internal notices are the classic fit.

Use a shared mailbox when

A small team needs to read and answer email sent to one address — support@, info@, finance@ — and reply as that address. It is the simplest way to turn a role-based address into a team inbox, and it needs no license under 50 GB.

Use a Microsoft 365 Group when

The same team also collaborates on documents, a calendar, or Planner tasks, or already has a group for Teams. Reusing that group for email keeps membership in one place and unlocks the wider Microsoft 365 toolset.

Whichever you pick, the moment more than a couple of people share the inbox you hit the same wall: no way to see who owns an email, whether it's been answered, or who touched it last. That's the gap SBX fills — it layers ownership, status, and history onto your existing shared mailbox or Microsoft 365 Group, right inside Outlook, with no separate helpdesk to learn.

Frequently asked questions

For Microsoft's own reference, see Compare groups in Microsoft 365 and About shared mailboxes.