Understanding Shared Mailbox Limitations in Office 365

Shared mailbox in Exchange Online allow a group of users to view and send email from a common mailbox. Understanding shared mailbox limitations in office 365 is important for setting up right expectations for customers. A lot of customers asked questions about utilizing shared mailboxes in office 365. Before we suggest a solution to the customers we should have a strong understanding of shared mailbox limitations in office 365. In this blog post, we will try to build an understanding on shared mailbox limitations to help customers in making a decision when to use a shared mailbox versus user mailbox.

Understanding Shared Mailbox Limitations in Office 365

A shared mailbox in office 365 is:

  • Free and do not require a license, but every user that accesses the Shared Mailbox must be assigned an Office 365 license.
  • Cannot be accessed by users with Exchange Online Kiosk license.
  • Can be used to store emails sent to and received by the Shared Mailbox.
  • Can be used to store data migrated from on-premises Public Folders.
  • Each shared mailbox can be a maximum size of 50GB but shared mailboxes over 50GB in size need to be licensed.
  • A Shared mailbox doesn’t have a username and password and users cannot log into it directly. A user must sign in to his/her own mailbox and then open the shared mailbox using permissions.

Shared mailboxes aren’t primarily associated with individual users and are generally configured to allow access by multiple users e.g. departmental users, Sales team, HR etc.

  • Cannot be used to archive emails from a user.
  • Cannot be used for Journaling.
  • Cannot be accessed using ActiveSync clients.
  • Doesn’t support Unified Messaging feature.
  • Cannot be accessed using Outlook client. To access a shared mailbox on outlook client, you need to first configure a user mailbox that has access to shared mailbox.
  • Active Directory user associated with a shared mailbox is always a disabled user account.

Create a Shared Mailbox in Office 365 using EAC:

To create a shared mailbox in office 365 using EAC, we need to follow the steps mentioned below.

  1. Log on to Office 365 Admin Center using Global Admin credentials.
  2. Go to Exchange Online Admin Center –> Recipients –> Shared and Click on + iconCreate a shared mailbox
  3. Enter Shared Mailbox information. Add users to Shared Mailbox that will have permissions to view and send email from shared mailbox.

Create a Shared Mailbox in Office 365 using Remote PowerShell:

To create a shared mailbox in office 365 using Remote PowerShell, Follow the steps mentioned below.

  1. Connect to Exchange Online PowerShell.
  2. After connecting to Exchange Online PowerShell, Run the cmdlet New-Mailbox -Name “Shared Mailbox Name” -Alias “Shared Mailbox Alias” -SharedPS
  3. Once the mailbox is created, Run the cmdlet to assign appropriate permissions to users. Add-RecipientPermission “MSTechTalk Shared” –Trustee riaz –AccessRights SendAs. This cmdlet will assign “Send As” permissions to user Riaz.


You can find more information on Exchange online limitations at TechNet.


  • Is in place archiving supported for shared mailboxes in Office 365. I’ve recently set this up in Exchange 2013 on premise. My results have been mixed. While I can archive, I can only view the shared mailbox archive in an Outlook client and not webmail. Just thought I’d see if there were limitations placed in Office 365.



    • Bryan,

      In place archive is supported in shared mailbox on office 365 and accessible in Office 365 OWA as well. I will perform one more testing with In Place archiving on shared mailbox and access the archive from OWA and will share my results with you. Thanks.

  • Nice job Riaz.

    One quick correction though; “Each shared mailbox can be a maximum size of 50GB” is correct, but shared mailboxes over 10GB in size need to be licensed.

    • Thanks Nathan but now the updated quota limit is 50GB. If your mailbox is greater then 50GB in size then you need to assign them a licenses. Previously it was 10GB limit.

  • “Each shared mailbox can be a maximum size of 50GB but shared mailboxes over 10GB in size need to be licensed”

    Can you please explain this a little more?

    As I read it a Shared Mailbox has a 50GB limit, but if it gets over 10GB’s it needs a license. I am not following as all O365 licenses are per user. How would you apply a license to a shared mailbox?
    Thanks for any information.

  • Woderful blog you have here but I was curious if you knew of any discussion boards that cover the same topics discussed here?
    I’d really love to be a part of community where I can get advice from other experienced individuals that share the same interest.
    If you have any recommendations, please let me know. Bless you!

  • Katherin,

    There are a lot of pages and groups available on linkedin and facebook which share the same interest. You can also join “Office 365 PK User Group” or “MS Tech Talk” Group on linkedin and our page on facebook “MS Tech Talk” to stay up to date with latest information on Microsoft technologies. Thanks.

  • Hi Riaz,
    Good article..however one think to add…it is possible to directly log into a shared mailbox using OWA… If you use the following link format http://outlook.office365.com/address@domain.x for example if the shared mailbox email address was shared@domain.x then browse to http://outlook.office365.com/shared@domain.x and enter your login details and you get logged straight in ( presuming you have full access permissions)

  • Also for Outlook a profile can be configured for a shared mailbox. When creating the profile put in the shared mailbox name for the email address but put in the users upn and password as the credentials. Then the profile will be created to access the mailbox using the user that has the full credentials to the mailbox. When the user opens Outlook they can then select if they want to log straight into the shared mailbox 🙂

  • Patrick,

    Appreciate your feedback on Shared mailboxes. Yes you can directly access the shared mailbox and configure the shared mailbox in outlook but it’s not recommended. Think about a sales or marketing user who don’t have technical expertise and he/she don’t know the exact email addresses of shared mailbox but again it’s a do able option but not recommended 🙂

  • Patrick,

    Also, you can configure shared mailbox on activesync device as well with the same steps that you shared regarding outlook client. Thanks.

  • ActiveSync configuration is as below.

    Enter your shared mailbox email address and password of account that has permissions to access the shared mailbox. On next page enter the username and password of account that has permissions and then update server address to outlook.office365.com and click next. It will setup your shared mailbox on active sync device. Thanks.

  • If we converted users mailbox to shared mailbox, Will each user need their own mailbox?