A shared mailbox is one inbox several people work in, and almost every small team runs theirs the same way: one password, sitting in a shared vault — or, more often, in a pinned message somewhere. It works, in the sense that mail gets answered. It also means there's no record of who did what, no way to remove one person's access without a rotation that disrupts everyone, and nothing stopping a departing employee from keeping a copy of the credential.
The alternative is delegated access: the shared mailbox has no password at all, and each team member reaches it with their own credentials. The mail app connects as you, and the shared mailbox appears as a folder alongside your own.
A delegated shared mailbox works in Outlook, Apple Mail, Thunderbird, mobile mail apps, and anything else that speaks IMAP. This article covers how it works, the one step everybody gets wrong, and what each permission level actually allows.
Four Ways Teams Do This
| Approach | What goes wrong |
|---|---|
| Shared password | No audit trail, no per-person revocation, a rotation every time someone leaves, and it breaks two-factor authentication entirely |
| Forward to everyone | Everyone gets a private copy, so nobody can see that a colleague already replied. Replies come from personal addresses. Authentication breaks on the forward. |
| Distribution list | Same problem, plus no shared archive — the history lives scattered across individual mailboxes and leaves with the people |
| A helpdesk product | Works well, and costs per agent per month for a team of three answering nine messages a day |
What a Delegated Shared Mailbox Actually Is
A shared mailbox is a real mailbox on the server with real storage and a real address. What it doesn't have is a login. Direct sign-in to a shared address is disabled on purpose — there's no password to leak because there's no password.
Access is granted by membership. Add a regular mailbox as a member and the server writes an IMAP access-control entry on the shared mailbox granting that mailbox's owner the rights you selected. When that person's mail app connects with their own credentials, the server includes the shared mailbox in the folder tree it advertises, under a delegated namespace:Shared/support@example.com/INBOX
Shared/support@example.com/Sent
Shared/support@example.com/ArchiveMost clients render that as a collapsible Shared → support@example.com → Inbox node in the sidebar.
Everything follows from there. Remove a member and the entry is revoked; their next connection simply doesn't include the folder, with no password change and no disruption to anyone else. Two-factor authentication keeps working, because each person is still authenticating as themselves. And because there's one copy of each message, a colleague marking something read is visible to the whole team — which is the entire point of a shared inbox and the thing forwarding can never provide.
Connecting It in a Mail App
The instruction that matters most is a negative one: don't add the shared address as a second account. That's the reflex, it will fail authentication, and the failure message won't explain why.
- Add your own mailbox to the app, using your own address and mailbox password. Take the server settings from Settings → Apps & devices rather than guessing — that page shows the values for your account and won't display them until sending and receiving are both ready.
- Wait for the membership to become active. Access is provisioned on the server and retried until it succeeds; Apps & devices reports when native mail-app access is ready for each shared mailbox.
- Refresh the app's folder list. Many clients cache the folder tree from when the account was added, so the shared node won't appear until you refresh, reconnect, or visit the app's folder-subscription screen.
The standard settings, for reference:
| Setting | Incoming | Outgoing |
|---|---|---|
| Protocol | IMAP | SMTP |
| Server | imap.trekmail.net | smtp.trekmail.net |
| Port | 993 | 465 (SSL/TLS) or 587 (STARTTLS) |
| Username | Your own mailbox address | Your own mailbox address |
| Password | Your own mailbox password | Your own mailbox password |
Note that the username is yours in both columns, including the outgoing one. That isn't a simplification for the table — it's how it works. See shared mailboxes in mail apps for the per-client walkthrough.
Sending as the Shared Address
Members with Can reply may put the shared mailbox address in the From field. The SMTP session still authenticates as the member's own mailbox; the server checks that this member is permitted to send as that address and accepts it.
If the shared address doesn't appear in your app's From menu, add it as a sending identity or alias on your existing account. Don't create a second account for it. In Apple Mail that's an extra address in the account's Email Address field; in Thunderbird it's Account Settings → Manage Identities; in Outlook it's the From dropdown once the address is known.
An app rejecting Send As almost always means one of three things: SMTP is authenticating with the shared address instead of yours, the shared address was added as a separate account, or Can reply was turned off.
The Step Everybody Gets Wrong
Sending a message and saving a copy of it are two entirely separate operations, and only the first one is SMTP's job.
SMTP hands the message to the server for delivery and that's the end of its involvement. The copy in your Sent folder is put there afterwards by your mail app, over IMAP, as a separate APPEND. The app decides which folder — and by default it picks your Sent folder.
The result is the classic complaint: "I replied to the customer but nobody else on the team can see it." The reply went out. The record of it landed in a personal Sent folder that the rest of the team can't open.
The fix is to configure the shared identity to save sent messages to the shared tree:
Shared/support@example.com/SentEvery client that supports multiple identities supports a per-identity Sent folder. Set it once when you add the identity. A member with Can reply may create that folder if it doesn't already exist.
Webmail doesn't have this problem — it writes the copy to the shared Sent folder automatically, because it knows which mailbox you were acting as. This is purely a desktop and mobile client concern.
Permissions
Membership is managed on the shared mailbox's Access tab, which is the single source of truth. Don't edit server-side access control lists by hand — they're reconciled from the membership list and manual edits are overwritten.
| Permission | Grants |
|---|---|
| Read-only membership | Open and read messages in the shared tree. Changes are rejected. |
| Can reply | Everything above, plus send as the shared address, mark read and starred, create folders, archive, move, copy, delete, and expunge — including moving messages between personal and shared folders. |
Removing a member revokes both the delegated folder and the Send As permission in one step.
Client Behaviour Worth Knowing
Archive and Junk buttons may not map correctly. Mail apps bind those toolbar buttons to the account's own special folders. In a shared tree the app may not work out that Shared/support@example.com/Archive is the intended target, so it archives into your personal Archive instead. Point the identity at the shared folders explicitly, or move messages by hand.
Moving to Junk isn't the same as reporting spam. Dragging a message into a Junk folder is a folder operation and nothing more. It doesn't train the server's spam classifier. If you want the classifier to learn, use Report spam in webmail, which does both.
Folder subscriptions cache aggressively. When access changes, apps that were already open frequently keep the old tree indefinitely. Reconnecting the account is the reliable fix.
Forwarding from a mail app isn't mailbox forwarding. Clicking Forward sends one message. Automatic forwarding of everything that arrives is a dashboard setting on the mailbox. They are unrelated, and confusing the two is how mail ends up going somewhere nobody intended.
One thing a shared mailbox does not do is schedule mail for later — see scheduled send for why a message queued from a team inbox has no clear owner when it fires.
Limits
| Plan | Shared mailboxes per domain |
|---|---|
| Nano | Not available |
| Starter | 5 |
| Pro | 15 |
| Agency | 30 |
Members aren't charged as seats. A shared mailbox with nine members costs the same as one with two, because it's one mailbox — which is precisely the difference from per-agent helpdesk pricing.
Frequently Asked Questions
Do I need the shared mailbox password?
There isn't one. Direct sign-in to a shared address is disabled by design. You connect with your own mailbox credentials and the shared inbox appears in your folder tree because your membership grants it.
Does this work in Outlook?
Yes, over IMAP. Add your own mailbox as an IMAP account and the shared tree appears under Shared. Note this is delegated IMAP access, not Exchange delegation — Outlook's Exchange-specific shared-mailbox UI isn't involved.
Why can't my colleague see the reply I sent?
Your mail app saved the copy to your personal Sent folder. Set the shared identity's Sent folder to Shared/<address>/Sent. Sending and saving the copy are separate operations, and only the app controls the second one.
Can two people work in a shared mailbox at the same time?
Yes. There's one copy of each message, so read and starred states are shared immediately — if a colleague opens a message, you see it as read. That visibility is the reason to use a shared mailbox rather than forwarding.
Does a shared mailbox count against my mailbox limit?
It's a mailbox, so it occupies one slot on the domain, and shared mailboxes are separately capped per plan. Members don't consume additional slots.
Can I turn an existing mailbox into a shared mailbox?
Yes, and back again. Converting keeps the stored mail; it changes how access works. A converted mailbox loses its own login, so make sure nobody is still signing in with it before you convert.
What is the difference between a shared mailbox and an alias?
An alias is an extra address that delivers into an existing mailbox — one person's inbox, one more label on it. A shared mailbox is separate storage with its own members and its own archive. If two or more people need to see the same messages, you need the second one.
