Creating and Managing Shared Mailboxes in Office 365

Shared mailboxes in Office 365 allow multiple users to access and manage emails from a single mailbox, making them ideal for team communication and customer support. This guide explains how to create, configure, and manage shared mailboxes in Office 365.

Requirements

• Admin access to the Microsoft 365 Admin Center
• An Office 365 license for users who will access the shared mailbox (though the mailbox itself does not require a license under 50GB)

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Step 1: Create a Shared Mailbox

Using the Microsoft 365 Admin Center

1. Log into the Microsoft 365 Admin Center

   • Go to https://admin.microsoft.com and sign in with your admin credentials

2. Navigate to Shared Mailboxes

   • In the left-hand menu, go to Teams & groups > Shared mailboxes

3. Create a New Shared Mailbox

   • Click + Add a shared mailbox
   • Enter a Name and Email address for the shared mailbox (e.g., [email protected])
   • Click Save changes

4. Assign Users to the Shared Mailbox

   • After creating the mailbox, click Edit under Members
   • Click + Add members and select the users who need access
   • Click Save to apply the changes

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Step 2: Configure Shared Mailbox Settings

Grant Additional Permissions

By default, users added to a shared mailbox have Full Access and Send As permissions. If you need to modify these permissions:

1. In the Shared mailboxes section, select the mailbox you created
2. Click on Manage mailbox permissions
3. Assign permissions as needed:
   • Full Access: Allows users to open and manage emails in the shared mailbox
   • Send As: Users can send emails as if they were the shared mailbox
   • Send on Behalf: Emails will show "sent on behalf of" the shared mailbox
4. Click Save to apply the changes

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Step 3: Access the Shared Mailbox

In Outlook Web App (OWA)

1. Log into https://outlook.office.com
2. Click on your profile picture at the top-right and select Open another mailbox
3. Enter the name of the shared mailbox and click Open

In Outlook Desktop App

1. Open Outlook and go to File > Account Settings > Account Settings
2. Select your account and click Change > More Settings
3. Navigate to the Advanced tab and click Add
4. Enter the shared mailbox email address and click OK
5. Restart Outlook, and the shared mailbox will appear in the left-hand panel

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Step 4: Convert a Regular Mailbox into a Shared Mailbox (Optional)

If you need to convert an existing user mailbox into a shared mailbox:

1. Go to Users > Active users in the Admin Center
2. Select the user whose mailbox you want to convert
3. Click Convert to shared mailbox and confirm
4. Remove the Office 365 license if the user is no longer active (shared mailboxes do not require a license unless over 50GB)

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Managing Shared Mailbox Storage

Shared mailboxes have a 50GB storage limit by default. If you exceed this limit:

• The mailbox will stop receiving new emails
• You'll need to either clean up old emails or assign an Exchange Online license to increase capacity

Storage management tips:

• Regularly archive or delete old emails
• Remove large attachments and save them to SharePoint or OneDrive
• Monitor mailbox size using PowerShell: Get-MailboxStatistics -Identity "[email protected]"

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Best Practices

✅ Grant access only to users who need it - Follow the principle of least privilege ✅ Regularly review permissions - Remove access for users who no longer need it ✅ Use descriptive names - Make it clear what the shared mailbox is for (e.g., "Sales Team" not "Mailbox1") ✅ Enable Send As permission carefully - Only grant to trusted team members ✅ Monitor mailbox size - Set up alerts before reaching the 50GB limit ✅ Document ownership - Assign a team owner responsible for managing the shared mailbox

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Troubleshooting

Shared mailbox not appearing in Outlook

• Wait 15-30 minutes for synchronization
• Restart Outlook
• Verify the user has Full Access permission
• Try adding the mailbox manually using the "Open another mailbox" option

Cannot send emails from shared mailbox

• Verify the user has Send As or Send on Behalf permission
• In Outlook, go to New Email > From and select the shared mailbox address

Mailbox exceeds 50GB

• Archive old emails to PST files or enable In-Place Archive (requires license)
• Assign an Exchange Online license to the shared mailbox for expanded storage