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Microsoft 365 offers numerous advantages that significantly impact professional email communication. Users can access applications online or install MS Office applications as standalone software on their computers.

Business and enterprise-based plans include Exchange Online, empowering administrators to create various mailbox types. These mailboxes, in addition to user mailboxes, enhance communication efficiency.

Types of Office 365 Mailboxes

Microsoft Office 365 mailboxes can be confusing for many users. In this post, we aim to clarify the various Office 365 mailbox types and their practical applications, helping you utilize them more effectively.

Office 365 comprises six primary mailbox types, with some requiring payment while others are accessible for free.

  • Mailbox (Requires license)
  • Shared mailbox (Free)
  • Distribution Group (Free)
  • Office 365 Groups (Free)
  • Resource mailbox (Free)
  • Contacts (Free)

We will describe each of these mailbox types, and what is their proper use.


The initial mailbox type provided by default upon acquiring an Office 365 subscription, inclusive of Exchange Online, is the licensed mailbox requiring a login. Its purpose is for personal emails and other related items. In simpler terms, it’s the mailbox used for sending emails, attachments, and messages to others.

You can have a specific domain email address for your primary mailbox. It can either be ending with your organization’s name or anything else. For example, it could be

Shared Mailboxes

Shared mailboxes are typically established by the Office 365 admin, who subsequently adds users as members. The creation of a shared mailbox in Office 365 is entirely free and comes with storage capacity of up to 50 GB. Shared mailboxes simplify communication for specific groups, allowing them to collectively monitor and send emails from a shared email address.

Furthermore, when any member of the group responds to an email received in a shared mailbox, the sender’s address will display as the shared mailbox’s email address. Utilizing a Shared Mailbox is an effective strategy for preventing your primary inbox from becoming cluttered with unnecessary emails and spam messages.

A few points about Shared mailbox are:
  • Every user assigned to the shared mailbox will have full control over the mail, which means if any user in a shared mailbox deletes a message, moves an email, or replies to an email from the inbox, then it will be reflected across all the users
  • Every user in a shared mailbox can reply an email, and it will appear from the shared mailbox address in the receiver’s mailbox
  • When you receive an email in a shared mailbox, you will not get the “new email’ pop-up like your primary mailbox
  • If you use it without a license, you will get only 50 GB storage, and if the storage exceeds, then you will have to purchase an Exchange online license for it.
  • A shared mailbox can be opened on Outlook Web App or Outlook Desktop app if you have full permissions to the shared mailbox. These points define how a shared mailbox is completely different from a primary mailbox.
Distribution Groups

Distribution groups are created to add specific members related to a team or project and send them emails. Also, it is used to communicate with clients or customers with a single email. An email to the distribution group will be received by each member of the group (in their primary mailbox).

Office 365 Groups

Recently introduced by Microsoft, Office 365 Groups are designed to elevate collaborative work. To set up an Office 365 Group, you simply need to create a name and an email address and then allocate users to it. By utilizing Office 365 Groups, you gain access to a multitude of resources including a mailbox, shared calendar, cloud-based document library, planner, SharePoint site, and more.

Furthermore, Office 365 Groups offer the flexibility to invite external guests to join the group for discussions and collaboration. Accessible through various platforms such as Outlook 2016, Outlook Web App, Outlook 2016 for Mac, and Outlook on Mobile, Office 365 Groups provide a seamless experience across different devices and interfaces.

Resource Mailboxes

Also referred to as an Equipment mailbox or room mailbox, this mailbox type is primarily employed for reserving and coordinating rooms and equipment. For instance, a video conference room is a typical resource mailbox. When you include a resource mailbox in a meeting request or calendar item, it signifies that you are reserving that particular resource for the specified time slot.


Contacts in your Office 365 mailbox consist of external email addresses with pre-existing contact information included in the global address list. By adding an individual to Contacts, you gain the ability to include that person in a distribution group. For instance, if you need to send an email to an external contact using a distribution list, you must first add their email address as a contact and then include them in the distribution group.


Office 365 stands out as a premier cloud platform, offering remarkable flexibility in managing email communication efficiently. To harness its capabilities effectively, it’s crucial to understand the diverse mailbox types and their applications. In this article, we’ve explored the various mailbox options within Office 365. Despite Microsoft’s robust data security measures, it’s prudent in numerous scenarios to back up these mailboxes, encompassing user, shared, and group mailboxes. And this can be done using an efficient tool like Kernel Office 365 Backup & Restore.