A shared mailbox is a centralized inbox that multiple people can open, read, and reply from using a single email address. A distribution list is simply a forwarding mechanism that sends a copy of each incoming email to every member’s personal inbox. They both let you send email to a group address, but they work in fundamentally different ways and serve different purposes.
How Email Delivery Works in Each
When someone emails a distribution list, each member receives their own separate copy of that message in their personal inbox. It works like a mailing list: the distribution list address is just a shortcut that expands into individual deliveries. Members read and reply from their own accounts, and their replies go out under their own name. You cannot send email from the distribution list’s address.
A shared mailbox works differently. When someone emails a shared mailbox, one copy of the message lands in the shared mailbox’s own inbox. Anyone with access can open that inbox (typically through Outlook, where it appears alongside their personal mailbox) and read the same message. If a team member replies, they can send the response from the shared mailbox’s address, so the outside sender sees “Contoso Support” or “Billing Department” rather than an individual employee’s name. This requires Send As or Send on Behalf permissions, which an admin grants to specific users.
Where Messages Are Stored
A distribution list has no storage of its own. It does not have a mailbox, a calendar, or a contacts folder. Once the message is delivered to each member’s inbox, the distribution list’s job is done. If a member deletes that email, it disappears only from their inbox. Other members still have their own copies.
A shared mailbox has its own dedicated storage, including an inbox, sent items, folders, a calendar, and contacts. Messages live in that central location. If someone deletes an email from the shared mailbox, it is gone for everyone with access. Shared mailboxes can hold up to 50 GB of data without a license. To expand that to 100 GB, the shared mailbox needs an Exchange Online Plan 2 license.
Visibility and Collaboration
This is where the practical gap between the two gets significant. In a shared mailbox, every team member sees the same inbox. If one person reads a message, it shows as read for everyone. If someone moves a conversation into a “Resolved” folder, the rest of the team sees that too. This makes it easy to coordinate who is handling what, especially for customer-facing functions like support queues or general inquiry addresses.
With a distribution list, each member works in isolation. You have no way of knowing whether a coworker already replied to a customer’s question, because their reply went out from their own address and lives only in their own sent folder. There is no shared view of the conversation history, no shared folders, and no way to organize incoming messages as a team.
What Happens When New Members Join
When you add someone to a shared mailbox, they immediately gain access to everything already in it: past emails, folder structures, calendar entries, and contacts. The full history is sitting in the shared mailbox, and the new member can browse it on day one.
Adding someone to a distribution list gives them nothing from the past. They will receive future messages sent to the list, but all previous emails were delivered to other members’ personal inboxes. The distribution list never stored those messages, so there is nothing to hand over.
Licensing and Cost
Distribution lists do not require a separate license. They are a basic feature of Exchange Online and Microsoft 365 and cost nothing beyond the licenses your users already have.
Shared mailboxes also do not require their own license in most cases. Each user who accesses the shared mailbox needs a licensed Exchange Online account, but the shared mailbox itself is free up to 50 GB. You only need to assign a license to the shared mailbox in specific situations: if you need more than 50 GB of storage, if you want to enable an in-place archive, if you need to place the mailbox on litigation hold, or if you want to apply advanced security or compliance features like retention policies or eDiscovery.
When to Use Each One
A distribution list is the right choice when you need to broadcast information to a group and no collaboration is required afterward. Company announcements, department-wide notifications, building or floor lists, and internal newsletters are all good fits. The message goes out, people read it, and nobody needs to coordinate a response.
A shared mailbox is the right choice when multiple people need to manage incoming messages together. Support desks, sales inquiry addresses, reception desks, HR inboxes, billing departments, and any “info@” or “hello@” address where customers expect a reply from the team rather than an individual person are classic use cases. The shared inbox, Send As capability, and message history make it possible for a team to take turns handling requests without dropping anything or sending duplicate replies.
If your situation falls somewhere in between, ask one question: does someone need to reply from a team address, or does the group just need to receive the same information? If the answer is “reply from a team address,” you want a shared mailbox. If the answer is “just receive,” a distribution list will do the job with less setup.