How to Set Up a Shared Mailbox in Microsoft 365 for Your Team

A shared mailbox lets multiple people read and send email from a common address like info@yourcompany.com or support@yourcompany.com without needing an extra license. Creating one takes about five minutes in the Microsoft 365 admin center.

What You Need

• Global Administrator or Exchange Administrator access to Microsoft 365
• The email address you want for the shared mailbox (e.g., info@, support@, sales@)
• A list of users who need access

Shared Mailbox vs. Distribution Group

These solve different problems. Pick the wrong one and you will end up reconfiguring later.

If you need a shared inbox where the team collaborates on replies, use a shared mailbox. If you just need to broadcast messages to a group, use a distribution group.

Step 1: Create the Shared Mailbox

1. Sign in to the Microsoft 365 admin center
2. In the left sidebar, go to Teams & groups > Shared mailboxes
3. Click + Add a shared mailbox
4. Enter a Display name (e.g., "Athencia Support")
5. Enter the Email address (e.g., support@yourcompany.com)
6. Click Save changes

The mailbox is created immediately. No license is needed — shared mailboxes are free and include 50 GB of storage. If you need more than 50 GB, you can assign an Exchange Online license to the shared mailbox later.

Step 2: Add Members

Members are the users who can read and send email from the shared mailbox.

1. After creating the mailbox, you will see it listed on the Shared mailboxes page
2. Click the shared mailbox name to open its settings
3. Under Members, click Edit
4. Click + Add members
5. Select the users who need access and click Save

Understanding Permission Types

When you add a member through the admin center, they get Full Access and Send As permissions by default. Here is what each means:

• Full Access: The user can open the shared mailbox and read, delete, and organize messages inside it. The mailbox appears in their Outlook automatically.
• Send As: The user can compose new messages that appear to come from the shared mailbox address. The recipient sees "support@yourcompany.com" as the sender with no indication it came from an individual.
• Send on Behalf (not granted by default): The message shows "User Name on behalf of support@yourcompany.com." This is useful when you want recipients to know which individual sent the message. To grant this, use the Exchange admin center or PowerShell.

For most teams, the default Full Access + Send As permissions are what you want.

Step 3: Access the Shared Mailbox in Outlook

Outlook Desktop (Windows/Mac)

The shared mailbox should appear automatically in the left folder pane within 15–60 minutes of being added as a member. If it does not appear:

1. Close and reopen Outlook
2. If it still does not appear, add it manually:
   • Click File > Account Settings > Account Settings
   • Select your email account and click Change
   • Click More Settings > Advanced tab
   • Click Add and enter the shared mailbox email address
   • Click OK through the dialogs and restart Outlook

Outlook on the Web

1. Sign in to outlook.office.com with your own account
2. Right-click Folders in the left sidebar
3. Select Add shared folder
4. Type the shared mailbox email address and click Add

The shared mailbox will appear as a separate mailbox in your folder list.

Outlook Mobile (iOS/Android)

The Outlook mobile app does not display shared mailboxes as a separate folder the way desktop Outlook does. To access it on mobile:

1. Open the Outlook app
2. Tap your profile icon in the top left
3. Tap the + (add account) icon
4. Select Add a Shared Mailbox
5. Enter the shared mailbox email address

This adds the shared mailbox as a separate account you can switch to. You will not see it merged into your primary inbox.

Step 4: Configure Sent Items

By default, when a user sends a message from a shared mailbox, the sent message is saved in the user's personal Sent Items folder — not the shared mailbox's Sent Items. This means other team members cannot see what has been sent, which defeats the purpose of a shared mailbox.

To fix this:

1. Sign in to the Exchange admin center
2. Go to Recipients > Mailboxes
3. Click the shared mailbox name
4. Click Delegation
5. Under Sent Items, enable both:
   • Copy sent items to the shared mailbox's Sent Items folder for Send As
   • Copy sent items to the shared mailbox's Sent Items folder for Send on Behalf
6. Click Save

After enabling this, sent messages will appear in both the user's personal Sent Items and the shared mailbox's Sent Items. This gives the entire team visibility into what has been sent.

Step 5: Set Up Auto-Replies (Optional)

If the shared mailbox receives inquiries from customers or vendors, you may want an auto-reply to confirm receipt.

1. In the Exchange admin center, go to Recipients > Mailboxes
2. Click the shared mailbox
3. Click Mail flow settings
4. Under Automatic replies, click Manage
5. Toggle on Send automatic replies
6. Enter your message (e.g., "Thank you for reaching out. Our team will respond within one business day.")
7. Set date ranges if you only want auto-replies during specific periods
8. Click Save

Common Issues

Need Help?

If you run into issues setting up or managing shared mailboxes, contact Athencia. We handle Microsoft 365 configuration as part of every onboarding.