Distribution List vs Shared Mailbox: The Difference, and When Neither One Is Enough

A distribution list forwards a copy of every message to each member's own mailbox. A shared mailbox is a single mailbox with its own address that several people open, read and reply from, so there is one copy of the conversation and everyone sees the replies. Use a distribution list for one-way announcements to a group of people. Use a shared mailbox when the group has to answer the mail and needs to see what teammates already said.

That is the whole distinction in four sentences, and it is enough to settle most cases. What it does not tell you is the part that causes trouble later: Microsoft caps a shared mailbox at 25 users, you cannot stop people deleting messages in one, and mail sent from one cannot be encrypted. Those limits decide when a shared mailbox stops being the right answer, and a lot of teams find out the hard way. Here is the full comparison, the two options most people forget, and the point where you have outgrown both.

What is a distribution list?

A distribution list, also called a distribution group, is an address that exists only to fan mail out. Someone emails [email protected], and Exchange or Google looks up the members and drops a separate copy into each of their personal mailboxes. There is no storage behind the address itself. Nothing is kept, because nothing arrived anywhere except in the members' own inboxes.

That design has two consequences worth understanding before you pick one. First, replies come from the individual, not the group. When Dana answers, the customer sees Dana's personal address and any further replies go to Dana alone, invisible to everyone else on the list. Second, there is no history. Add a new person to the list on Tuesday and they see nothing that arrived before Tuesday, because those copies went to other people's mailboxes and were never held centrally.

For announcements, that is all fine and arguably ideal. all-staff@, engineering@ or board@ as a way to reach a set of people works exactly as intended. For anything that needs answering, both consequences turn into problems fast.

What is a shared mailbox?

A shared mailbox is a real mailbox with its own address and its own storage, which multiple licensed users are granted permission to open alongside their own. It appears in the folder list in Outlook automatically once permission is granted. Everyone sees the same inbox, the same read and unread state, and the same Sent Items, so a reply Dana sends is visible to the whole team.

Members can be given Send As permission, which makes replies appear to come from [email protected] rather than from Dana, or Send on Behalf, which shows both names. That single feature is usually the reason teams move off a distribution list: customers get a consistent address to reply to, and the conversation stays in one place.

The licensing is more generous than people expect. Microsoft states that a shared mailbox can store up to 50 GB without any license assigned to it. You do need a licensed Exchange Online mailbox of your own to access one, and going beyond 50 GB, adding a larger archive or placing the mailbox on litigation hold each require an Exchange Online Plan 2 license or Plan 1 with the archiving add-on. But for a small team, the shared address itself is effectively free, which makes it the correct first thing to try.

Distribution list vs shared mailbox: the difference at a glance

The last two rows are the ones people skip and then regret. Neither option answers "who is handling this one". That question is what separates both of them from actual shared inbox software.

What about Microsoft 365 Groups and Google Groups?

These are the two options that rarely come up in the comparison and often turn out to be the right answer.

A Microsoft 365 Group gives shared access to email and a calendar, plus a shared workspace, and it uses a different model from a shared mailbox. Microsoft's own guidance points you toward a group in two specific cases where a shared mailbox cannot help: when you need to stop people deleting messages, which a shared mailbox genuinely cannot do, and when you need to give access to someone outside your organization, which a shared mailbox does not permit at all. If either of those matters, the decision is already made for you.

On the Google side, a collaborative inbox in Google Groups is the closest equivalent to a shared mailbox. It goes further than either Microsoft option in one respect: members can assign a conversation to a specific person and mark it resolved. That is genuinely the assignment feature a shared mailbox lacks. It is basic compared with paid software, and the interface is a weak point, but for a Workspace team that wants shared handling at no extra cost it is worth an afternoon of testing before spending anything.

The four limits that decide when you have outgrown a shared mailbox

Microsoft documents these plainly, and read together they form a clean upgrade trigger.

1. 25 users maximum. Beyond that, Microsoft warns of connection failures and duplicated messages when too many people access the mailbox at once. It recommends a Microsoft 365 group instead.
2. You cannot prevent deletion. There is no way to stop a member deleting messages from a shared mailbox. On a mailbox that carries contracts, complaints or anything an auditor might ask about, that is a real control gap.
3. No encryption. Mail sent from a shared mailbox cannot be encrypted, because the mailbox has no security context of its own and so cannot hold an encryption key. If members encrypt using their personal keys, other members may not be able to read those messages.
4. No external access. Only people inside your organization can be given access. An outside bookkeeper, agency or contractor cannot be added, full stop.

One more worth knowing: never sign in directly to the shared mailbox's account. Every shared mailbox has an underlying user account with a system-generated password, and Microsoft's instruction is to block sign-in for that account and keep it blocked. Teams that share the password instead of granting permissions have created an unattributable shared login, which is exactly the thing security reviews flag.

How to choose, in order

Work down this list and stop at the first line that describes you.

• Nobody replies to the address, it just notifies people: distribution list.
• A few people answer it, replies should come from the group address, and you need shared history: shared mailbox, which costs nothing extra up to 50 GB.
• You need to prevent deletion, or an outsider needs access: Microsoft 365 Group, because a shared mailbox cannot do either.
• You are on Google Workspace and want basic assignment at no cost: collaborative inbox in Google Groups.
• You are near 25 people, or you need assignment, statuses, SLAs and reporting: you have outgrown all of the above and want real software.

That last line is the expensive one, so be honest about whether you are actually on it. The signal is not team size on its own. It is when nobody can answer "has anyone replied to this?" without asking out loud, when messages older than a day go unanswered because each person assumed someone else had it, or when you cannot report on how long customers waited. At that point the comparison you want is not this one, and we laid out the real options and their August 2026 prices in our guide to email management software, including the free tiers worth exhausting first.

Two mistakes worth avoiding

The first is converting a busy personal mailbox into a shared one when someone leaves. It is a supported operation and it is often the right call, but it hands everyone with access the departed employee's entire mail history, including anything personal, HR-related or confidential they ever received. Review the contents before you convert, not after.

The second is treating a shared mailbox as a filing system. Because it has generous storage and nobody owns it, shared mailboxes quietly accumulate years of mail that nothing else references, and then hit the 50 GB ceiling. Microsoft's behavior at that point is unkind: the mailbox keeps receiving for a while, then stops sending, then stops receiving entirely and senders start getting non-delivery receipts. Set a retention policy early rather than discovering the ceiling on a Monday morning.

Finally, a note on what none of this fixes. Choosing correctly between these four options controls where the mail lands and who can see it. It does nothing about the volume arriving, or about the work each message creates once someone has read it. If the underlying problem is that support@ generates more follow-up than the team can carry, that is a customer operations question rather than a mail routing one, and it is worth designing the workflow behind the inbox before adding software on top of it. On the mail side specifically, the follow-through half of the problem, chasing the people who never replied and booking the things the threads were negotiating, is covered on our follow-ups page.