Understanding Shared Mailboxes in Office 365 (updated)

Many potential customers are asking about departmental mailboxes in Office 365. How can a department, a team etc share a mailbox, and does it involve a license?

Shared mailboxes in Office 365 Exchange Online allow a group of users to view and send e-mail from a common mailbox.

A shared mailbox:

  • doesn’t have a username and password, so users cannot log on to it directly. A user must sign in to his/her own mailbox and then open the shared mailbox using Send As permissions
  • don’t require a license, but each user that accesses a shared mailbox must be assigned to a subscription plan
  • cannot be accessed by users with Exchange Online Kiosk subscriptions
  • has a maximum size of 5 GB. Exceeding this limit will require an Exchange Online plan 1 subscription (see Note 1 below )
  • 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
  • cannot be used to archive e-mails for individual users

In Office 365 Exchange Online, shared mailboxes are created only via Remote PowerShell. See the article "A couple of tips for setting up Shared Mailboxes" - link for more details. Update March 26th 2012 - new GUI based tool for creating Shared Mailboxes

Note 1 -- From an Exchange perspective a shared mailbox is just a 5GB mailbox provisioned to a disabled user account (and delegated to a bunch of SG/Users). So when reaching the quota, mailbox will start receiving warning messages (10% prior to the quota) and then will start blocking mail sent from it (if “send as” as been granted and ‘from”  used) and finally it will refuse accepted new e-mail (with “mailbox is full” in the NDR).


See also

Comments (20)
  1. 365Fanboy says:

    It is now possible to create a shared mailbox through the Office 365 web-based management portal.

  2. Salim says:

    I believe to open shared mailbox we need full access and not send as.

  3. guessingso says:

    You need both full access and send as access

  4. rodrigo says:

    Is this limit (5GB) still valid?
    I’ve found a 50GB limit on this article

  5. Tim says:

    10G is the limit for shared mailboxes

  6. bill says:

    The limit has been increased to 50 GB if you are using Office 365 shared mail files.

  7. T says:

    When creating shared mailbox through powershell it does create a rather lengthy smtp entry. check with
    (get-mailbox ).EmailAddresses
    use that email to login (password can be reset through admin portal)
    when logged it allows for password change as it were non-shared mailbox. hope that helps

  8. t says:

    that command again is: (get-mailbox your_shared_mailbox).emailaddress

  9. Greg Kirkman says:

    So it does have a password then?????????

  10. Patrick Gibson says:

    I’m having a hard time understanding how to actually use a shared mailbox. In the web version of Outlook, I managed to find that you could click on the profile image in the upper right, and "Open other mailbox…" where you have to type in the address
    of the mailbox you want to check. But this doesn’t seem to be a very practical way if one wants to be proactively notified of new messages.

    In the iOS version of Outlook, I can’t see anywhere at all where I could access the contents of a shared mailbox from the member account. Is this more of a Windows only feature?

  11. H says:

    @Patrick, You right click on the username on the left side then Add Shared folder…That way it will pin to left side below your mailbox.

  12. Dave says:

    Is it possible to access a shared mailbox from an iOS device?

  13. Rikard Strand says:

    Do you know if it’s still a valid point that K1 users cannot access the shared mailboxes?
    My testing shows that it works and I’m just wondering if anything has changed. Is it a technical limit or just a "license" limit ?

  14. shawn price says:

    can you use out of office on a group mailbox?

  15. William Bentley says:

    Can you access these shared mailboxes on mobile devices?

  16. Anonymous says:

    Not that I’m counting but I just realized one of my blog posts actually is closing in on 100k views

  17. GregT says:

    User is on Outlook 2010 and has delegate access to a shared mailbox. Every time we open Outlook the Shared Mailbox appears in the folder list AND the contents of the shared mailbox start downloading into the Outlook 2010 user’s OST file, so she soon maxes out her mailbox limit. How do we display the Shared mailbox but not have the shared mailbox email download to the user’s OST file?

  18. Dineshkumar R says:

    tell us, A user can be a part of how many Shared Mailbox, any restriction

  19. biz soibe says:


    will exchange create a user account in active directory for the shared mailbox?

  20. biz soibe says:

    also does the shared mailbox have complete mailbox functionality, such as a sent folder etc.?

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