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Difference between a User Mailbox and a Shared Mailbox

Updated: May 16

The main difference between a user mailbox and a shared mailbox is that the shared mailbox is associated with a disabled user. A shared mailbox is mainly used to allow multiple users login access. It is the same when multiple users simultaneously use a user mailbox and a shared mailbox.

A user mailbox can work as a shared mailbox if you grant full mailbox access permission to the other users on the user mailbox. These users can log onto the user mailbox. However, it is not recommended. For security concerns, if you want multiple users to log on to one mailbox, please use a shared mailbox.

User mailbox and  shared mailbox

User Mailboxes

A User mailbox usually involves a single user and requires a license. A mailbox is required for a user to log on to and use Office 365 email.

  • Mailboxes require a paid license.

  • Users need a mailbox to log in and use email.

Paid License Requirement

A paid license is mandatory to access and use a user mailbox in Office 365. Here are the key aspects of this requirement:

Access to Office 365 Suite

The paid license provides the user access to the entire Office 365 suite, including applications like Outlook, Word, Excel, and PowerPoint. This ensures that users can seamlessly integrate their email with other productivity tools.

Enhanced Features and Storage

Licensed user mailboxes typically come with larger storage capacities compared to unlicensed or shared mailboxes. This means users can store more emails, attachments, and calendar items without worrying about running out of space.

Security and Compliance

The paid license includes advanced security features such as data encryption, spam filtering, and phishing protection. This helps safeguard sensitive information and maintain compliance with regulatory standards.

Individual User Access

User mailboxes are designed for individual access, which comes with several benefits:

Personalized Email Management

Each user mailbox is associated with a single user, allowing for personalized settings and configurations. Users can customize their email experience according to their preferences, including setting up rules, filters, and automatic replies.

Privacy and Security

Since the mailbox is tied to an individual user, it provides higher privacy and security. Only the designated user can access the mailbox, reducing the risk of unauthorized access and data breaches.

Integration with Personal Calendars

Users can manage their calendars within their mailbox. This includes scheduling meetings, setting reminders, and sharing calendar events with colleagues. The integration ensures that users can coordinate their schedules effectively.

Professional Identity 

Having an individual mailbox helps maintain a professional identity for each user within the organization. Emails sent from a user mailbox are personalized with the user's name and email address, which is essential for professional communication.

Use Cases for User Mailboxes

Employee Communication

User mailboxes are ideal for individual employees who need their email accounts for daily communication, both within and outside the organization.

Executive Management

High-level executives often require dedicated mailboxes for managing sensitive communications, strategic planning, and confidential information.

Customer Support Representatives

Individual mailboxes can be used by customer support representatives to handle client queries, ensuring personalized and efficient customer service.

Shared Mailboxes

A shared mailbox is just that, a mailbox that can be shared with one or more users. Shared mailboxes do not require a license and have all of the features of a regular mailbox; they have an inbox, a calendar, a contact list, etc.

  • Shared mailboxes are not supported on mobile devices

  • Shared mailboxes appear as separate mailboxes in Outlook and Outlook on the web.

  • A user can send an email and have the message appear to come from the shared mailbox email address.

  • If a user replies to a message in a shared mailbox, the reply appears to come from the shared mailbox email address.

  • A user can also (if permission) send a message "on behalf of" a shared mailbox. The message will appear to come from "Jane Doe on behalf of <Shared Mailbox>"

  • Calendars and contact lists in shared mailboxes are fully useable by users having access to the shared mailbox.

  • Email sent from a shared mailbox does not appear in the sent items of the shared mailbox by default, but rather the sent items of the user sending the email message. This behaviour can be changed, however.

  • Shared mailboxes support subfolders, i.e. it is possible to create folders under inbox, for example, in order to organize email.

Key Features of a Shared Mailbox

No Individual License Requirement


Shared mailboxes do not require a dedicated license unless their storage exceeds 50GB. This makes them a cost-effective solution for teams needing shared email access without additional licensing costs.

Scalable Storage

If additional storage is needed, assigning an Exchange Online Plan 2 license can increase the mailbox size to 100GB, ensuring ample email and calendar data space.

Collaborative Email Management

Unified Inbox

Multiple users can access and manage emails from a single mailbox, ensuring all team members are on the same page. This is particularly useful for departments like customer support, sales, or project management.

Send As or On Behalf Of

Users can send emails from the shared mailbox address, making communication appear unified. They can also send on behalf of the shared mailbox, which shows transparency about who is sending the email.

Shared Calendar and Contacts

Team Calendar

The shared mailbox includes a calendar that all members can access. This feature simplifies scheduling team meetings and events and managing group tasks.

Contact Management

A shared contact list allows team members to maintain and access a centralized database of important contacts.

Accessibility and Integration

Multiple Access Points

Shared mailboxes can be accessed via Outlook on the web, desktop, and mobile apps. This ensures that team members can stay connected and manage communications from anywhere.

Integration with Office 365 Tools

The shared mailbox seamlessly integrates with other Office 365 tools, enhancing productivity and collaboration.

Security and Compliance

Centralized Management

Administrators can easily manage permissions, ensuring only authorized users can access the shared mailbox. This helps maintain security and compliance standards.

Audit and Monitoring

Activities within the shared mailbox can be monitored and audited, providing transparency and accountability for all actions performed by team members.

Usage Scenarios for a Shared Mailbox

Customer Support Teams

Unified Response System

A shared mailbox allows customer support teams to manage and respond to customer queries from a single email address. This ensures that responses are consistent and can be tracked easily.

Improved Collaboration

Team members can see all customer interactions, allowing for better collaboration and quicker resolution of issues.

Sales Departments

Centralized Communication

Sales teams can use a shared mailbox to manage communication with clients. This ensures that all team members have visibility into ongoing conversations and can contribute as needed.

Consistent Client Interaction

Emails from the shared mailbox maintain a professional and consistent image for the company.

Project Management

Coordinated Efforts 

Project teams can use a shared mailbox to coordinate efforts, share updates, and manage project-related communications. The shared calendar helps schedule meetings and track project milestones.

Task Delegation

Using the shared mailbox, project managers can delegate tasks and follow up on progress, ensuring everyone is aligned and informed.

Human Resources

Recruitment Management

HR teams can manage job applications and recruitment communication through a shared mailbox, ensuring all team members can access candidate information and collaborate on hiring decisions.

Employee Communication

A shared mailbox can be used to efficiently disseminate important HR updates, policies, and announcements to all employees.

The Difference

If a user replies to a message in a shared mailbox, the reply appears to come from the shared email address.

Email sent from a shared mailbox does not, by default, appear in the items sent to the shared mailbox but rather in the items sent by the user sending the email message. This behaviour can be changed. However, shared mailboxes support subfolders, i.e., creating folders under inbox to organize email is possible.

A regular mailbox, by default, goes to the user.

  • You can't log into a shared mailbox, so it can't be the Outlook profile mailbox, but it can be added as an additional mailbox.

  • You cannot set a shared mailbox as a primary profile in Outlook.

  • Anyone with permission to access the shared mailbox can access it with Outlook and OWA. If the user also has Send As permission, they can select the mailbox name for the To: field when they send the message.

  • You can add the Automapping $True switch when you grant the user permission to access the mailbox.

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