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Summary
There are many ways to give someone access to email in Microsoft 365 — shared mailboxes, delegated access, Send As, Send on Behalf, forwarding, distribution lists, and Microsoft 365 Groups. This article explains each type, when to use it, and how they differ so you can request the right access or understand what you already have.
Before You Start
- A Microsoft 365 mailbox.
- Some access types require an IT administrator to configure. This article notes which ones.
Instructions
1. The Six Mailbox Access Methods at a Glance
Use this table to quickly compare every way email access is granted in Microsoft 365.
| Method | What It Does | Who Sets It Up | Needs Its Own License? | Appears in Your Outlook? | Sent Mail Shows As |
|---|---|---|---|---|---|
| Shared Mailbox | A group inbox (e.g., [email protected]) that multiple people can read and send from | IT Admin | No (up to 50 GB free) | Yes — auto-mapped or added manually | The shared mailbox address |
| Full Access (Delegation) | Read and manage another user's entire mailbox (e.g., your manager's inbox) | IT Admin | No (uses the other user's license) | Yes — auto-mapped or added manually | Depends on Send As / Send on Behalf setup |
| Send As | Send email that appears to come from another address — recipients cannot tell the difference | IT Admin | No | No folder access — only changes the "From" field | The other address (indistinguishable from the real owner) |
| Send on Behalf | Send email showing "Your Name on behalf of Other Address" | IT Admin or mailbox owner | No | No folder access — only changes the "From" field | "Your Name on behalf of Other Address" |
| Mail Forwarding | Automatically copy or redirect incoming mail to another mailbox | IT Admin, user (via rules), or both | No | No — mail arrives in your own inbox | Original sender (with "FW:" if forwarded by rule) |
| Distribution List (DL) | Deliver one email to many recipients at once | IT Admin or DL owner | No | No — each member receives mail in their own inbox | Each member replies from their own address |
| Microsoft 365 Group | A DL with shared resources — group mailbox, calendar, SharePoint site, Planner | IT Admin or allowed users | No | Optional — can be added to Outlook | Each member replies from their own address (or the group address if configured) |
2. Shared Mailbox — Deep Dive
A shared mailbox is the most common way to give a team a shared email address (e.g., [email protected], [email protected]).
How it works:
- IT creates the shared mailbox and adds members.
- Members see the shared mailbox appear in their Outlook folder pane (this is called auto-mapping).
- Members can read, reply, and send new email from the shared address.
- No one signs in directly to a shared mailbox — you access it through your own account.
Key facts:
- Does not require its own license (up to 50 GB). If it exceeds 50 GB, a license is required.
- Cannot be used to sign in to Teams, OneDrive, or other Microsoft 365 services.
- Supports Send As and Send on Behalf (configured separately by IT).
- Has its own Inbox, Sent Items, and folders — separate from your personal mailbox.
3. Full Access (Delegated Mailbox)
Full Access lets you open and manage another person's entire mailbox — read their email, reply, delete, and organize folders.
Common scenario: An executive assistant managing their manager's inbox.
How it differs from a shared mailbox:
- A shared mailbox is a "team" mailbox with no individual owner. Full Access gives you access to a specific person's mailbox.
- Full Access does not automatically grant the ability to send email from that mailbox — Send As or Send on Behalf must be granted separately.
Auto-mapping: By default, a mailbox you have Full Access to appears automatically in your Outlook folder pane. IT can disable auto-mapping, in which case you add it manually through File > Account Settings > Account Settings > Change > More Settings > Advanced > Add.
4. Send As vs. Send on Behalf
These two permissions control how email appears when you send from another address. They are often confused.
| Send As | Send on Behalf | |
|---|---|---|
| What the recipient sees | From: [email protected] — looks like it came directly from that address | From: Jane Doe on behalf of [email protected] |
| Can the recipient tell who actually sent it? | No — it is indistinguishable from the mailbox owner | Yes — both names are visible |
| Who can grant it? | IT Admin only | IT Admin or mailbox owner (in some configurations) |
| Where does Sent Mail go? | Sent Items of the sender's mailbox (not the shared mailbox, unless IT configures otherwise) | Sent Items of the sender's mailbox |
| Best for | Department addresses where individual identity is hidden (e.g., support@, billing@) | Executive assistants or anyone who need to be identified as sending on someone else's behalf |
How to use either permission:
- Create a new email in Outlook.
- Click From in the message header. If the From field is not visible, click Options > From.
- Select the address you want to send from, or type it manually.
- Compose your message and click Send.
5. Mail Forwarding
Forwarding automatically sends a copy of incoming email to another mailbox. There are three types:
| Type | Set Up By | How It Works | Keeps a Copy in Original Mailbox? |
|---|---|---|---|
| Server-side forwarding | IT Admin (Exchange Admin Center) | All mail is forwarded at the server level before it reaches Outlook | Configurable — can keep or not keep a copy |
| Inbox Rule forwarding | The mailbox owner (Outlook > Rules) | A rule forwards mail matching specific criteria | Yes — original stays in Inbox |
| Transport Rule redirect | IT Admin (Exchange Admin Center) | Mail is redirected at the organization level, often for compliance | Configurable |
Forward vs. Redirect:
- Forward sends the message as a forwarded email — the recipient sees "FW:" and the original sender info.
- Redirect changes the delivery path so the message appears as if it was sent directly to the new recipient. The original recipient may never see it.
When to use forwarding:
- Employee on extended leave — forward to a colleague.
- Monitoring a mailbox without giving Full Access.
- Forwarding is not a substitute for a shared mailbox — it only goes one direction and does not allow sending from the original address.
6. Distribution Lists vs. Microsoft 365 Groups
Both let you email a group of people with one address, but Microsoft 365 Groups include much more.
| Distribution List (DL) | Microsoft 365 Group | |
|---|---|---|
| What it does | Delivers email to all members | Delivers email + provides a shared calendar, SharePoint site, Planner board, and OneNote notebook |
| Shared mailbox | No — each member gets a copy in their own inbox | Optional — has a group mailbox members can access |
| Who can send to it | Anyone (or restricted by IT) | Anyone (or restricted) |
| Self-service join | Usually no — IT manages membership | Can be configured to allow self-service |
| Appears in Outlook | Only in the address book | Can be added to the Outlook folder pane |
| Replies go to | The original sender (not the group) | Configurable — can go to the group or the sender |
| Best for | Simple email broadcasting (e.g., all-staff@, marketing-team@) | Teams that need shared resources beyond email |
Choosing between them is a wider question than this table settles. Everything in this article is about how access is granted — who can open a mailbox and whose name lands on the reply. Deciding whether your team needs a distribution list, a Microsoft 365 Group, or a shared mailbox in the first place is a question about what the team has to do together, and Understanding Distribution Lists, Microsoft 365 Groups, and Shared Mailboxes works through it scenario by scenario, with the exact request to send IT for each.
7. Auto-Mapping vs. Manual Mapping in Outlook
When IT grants you access to a shared or delegated mailbox, it usually auto-maps — the mailbox appears in your Outlook folder pane automatically within 30–60 minutes.
When auto-mapping does not work:
- IT has disabled auto-mapping for that mailbox.
- You are using New Outlook or Outlook on the Web (auto-mapping behavior differs).
- The mailbox was recently added and has not synced yet.
How to manually add a mailbox:
| Client | Steps |
|---|---|
| Classic Outlook | File > Account Settings > Account Settings > select your account > Change > More Settings > Advanced > Add > type the mailbox address |
| New Outlook | Click your profile icon > Open another mailbox > type the address |
| Outlook on the Web | Click your profile icon > Open another mailbox > type the address > Open |
8. Which Access Type Should I Request?
Use this decision guide to determine what to ask IT for.
| I need to... | Request this |
|---|---|
Share a team inbox (e.g., support@, info@) | Shared Mailbox |
| Read and manage my manager's email | Full Access + Send on Behalf |
| Send email as a department address without revealing my name | Send As on a Shared Mailbox |
| Receive a copy of another mailbox's incoming email | Mail Forwarding |
| Email an entire department with one address | Distribution List or Microsoft 365 Group |
| Collaborate with a team (shared calendar, files, tasks, and email) | Microsoft 365 Group |
| Temporarily handle someone's email while they are away | Full Access (or Forwarding if read-only is enough) |
Troubleshooting
INFO
Most mailbox access changes take 30–60 minutes to take effect. If a mailbox does not appear after being granted access, restart Outlook and wait. If it still does not appear after 60 minutes, add it manually, or ask IT to confirm your account holds Full Access on that mailbox and that auto-mapping is switched on for it. Name the mailbox's exact email address in the request — that is what they search for.
| Symptom / Error | Potential Cause | Solution |
|---|---|---|
| Shared mailbox not appearing in Outlook | Auto-mapping not yet synced or disabled | Restart Outlook. If still missing after 60 minutes, add manually. See How to Add a Shared Mailbox in Outlook. |
| Can read mail but cannot send from the shared mailbox | Send As / Send on Behalf not granted | Contact IT to request Send As or Send on Behalf permissions. |
| Sent email shows my name instead of the shared mailbox | Using Send on Behalf instead of Send As | If you need recipients to see only the shared address, ask IT to grant Send As instead. |
| Sent email goes to my Sent Items, not the shared mailbox's Sent Items | Default Outlook behavior | Ask IT to enable the shared mailbox's option to copy sent messages into its own Sent Items, and give them the mailbox's exact email address. |
| "You don't have permission" when opening a mailbox | Access not yet granted or not yet synced | Verify with IT that your account was added. Wait 60 minutes and restart Outlook. |
| Forwarded mail missing from original mailbox | Redirect rule (not forward) is configured | A redirect removes the message from the original mailbox; a forward keeps a copy. Ask IT to convert the redirect into a forward, and provide the mailbox address and where the mail is going now. |
Related Articles
- How to Add a Shared Mailbox in Outlook
- Understanding Distribution Lists, Microsoft 365 Groups, and Shared Mailboxes
- How to Give a Coworker Access to Your Inbox or Calendar (Delegate Access)
- How to Manage Calendar Sharing Permissions in Outlook
- How to Create a Contact Group in Outlook
- How to Send, Reply, and Forward Email in Outlook
- How to Create Email Rules in Outlook
- Understanding Microsoft 365 Groups, Teams, and SharePoint Sites