Microsoft Exchange Server 2016: Site Mailboxes


In this tutorial we are going to learn about site mailboxes and how to use them.


  • Email and documents are traditionally kept in two unique and isolated separate data repositories. Mostly enterprises collaborate using both mediums. The main challenge is that both email and documents permitted being accessed using different clients. This usually results in a reduction in user productivity and a degraded user experience.

  • The site mailbox, introduced in Exchange 2013, is a solution for this problem. Site mailboxes enhance collaboration and user productivity by permitting access to both Microsoft SharePoint 2013 documents and Exchange email utilizing the same client interface.

  • A site mailbox is functionally composed of SharePoint 2013 site membership (members and owners), shared storage via an Exchange 2016 mailbox for email messages and a SharePoint 2013 site for documents, and a management interface which addresses provisioning and lifecycle requirements.

  • Site mailboxes need Exchange 2016 and SharePoint Server 2013 integration and configuration.


How do site mailboxes perform?

  • When single project member files mail or documents using the site mailbox, any project member is allowed to access the content.

  • Site mailboxes are surfaced over Outlook 2013 or later and provide users easy access to the email and documents for the projects they care about. Moreover, the same set of content might be accessed directly from the SharePoint site itself. With site mailboxes, the content is stored where it belongs.

  • Exchange saves the email, offering users with the same message view for email conversations which they use every day for their own mailboxes. Meanwhile, SharePoint saves the documents, getting document coauthoring and versioning to the table.

  • Exchange synchronizes sufficient metadata from SharePoint to create the document view in Outlook (e.g. document title, last modified author, last modified date, size).


Performance of site mailboxes


Site mailbox provisioning policies

  • Site mailbox quotas can fix and set by using the SiteMailboxProvisioningPolicy cmdlets over the Exchange Management Shell.

  • The Site mailbox provisioning policies is only applicable to the email that is sent to and from the site mailbox and the size of the site mailbox over the Exchange Server.

  • The document repository settings are configured in SharePoint. Though you are allowed to create multiple site mailbox provisioning policies using the New-SiteMailboxProvisioningPolicy cmdlet, and only the default provisioning policy is going to be applicable to all site mailboxes.

  • You can’t apply multiple policies within an organization. The provisioning policies allow you to set the following quotas:


Quota to be Set

Detail Description

Default setting


The IssueWarningQuota parameter mentions the site mailbox size which triggers a warning message to the site mailbox.

4.5 GB


The MaxReceiveSize parameter mentions the maximum size of email messages which can be received by the site mailbox.

36 MB


The ProhibitSendReceiveQuota parameter mentions the size at which the site mailbox might no longer send or receive messages.

5 GB


Lifecycle policy and retention

  • The lifecycle of a site mailbox is controlled and managed via SharePoint. It is through SharePoint that you must perform all site mailbox tasks like creating and removing site mailboxes. Further, you can create a SharePoint Lifecycle policy to control and manage the lifecycle of a site mailbox.

  • For instance, you can create a lifecycle policy in SharePoint which automatically closes all site mailboxes after six months. In case the user still needs the use of the site mailbox, the user can reactivate the site mailbox via SharePoint. We suggest that you use the Lifecycle application is in the farm. Manually removing active site mailboxes from Exchange is going to result in orphaned site mailboxes.

  • When the lifecycle application over the SharePoint closes a site mailbox, the site mailbox is retained for the period mentioned in the lifecycle policy in the closed state. The mailbox might then be reactivated by an end-user or by an administrator from SharePoint.

  • When the retention period is over, the Exchange site mailbox which is housed in the mailbox database is going to have its name prepone with MDEL: to depict that it has been marked for deletion. You require to manually deleting these site mailboxes from the mailbox database in context to free storage space and the alias.

  • In case you don’t have the SharePoint Lifecycle Policy enabled, you are going to lose the capability to determine which site mailboxes are marked for deletion. Till the site mailbox has been deleted by an administrator, the content of the mailbox is still recoverable.


You are allowed to use the following command to search for and remove site mailboxes which have been marked for deletion.


  • Get-Mailbox MDEL:* | ?{$_.RecipientTypeDetails -eq “TeamMailbox”} | Remove-Mailbox -Confirm:$false

  • Site mailboxes do not support retention at the item-level. Retention performs and works on a project-level for site mailboxes, such that when the entire site mailbox is removed, the retained items will be deleted.



  • Using the eDiscovery Console in SharePoint, site mailboxes can be part of the In-Place eDiscovery scope as you can do keyword searches against user mailboxes or site mailboxes. In addition, you can put a site mailbox on legal hold.


Backup and restore

  • Backup and Restore for the Exchange site mailboxes located on the mailbox server will use the same backup and restore strategy which you use for all Exchange mailboxes.

  • For SharePoint documents, you must backup and restore into the same location. In case you restore your SharePoint content to same URLs, then the site mailbox is going to continue to work and no additional configuration is required.

  • In case you restore to a different URL, then you are going to need to run and execute the Set-SiteMailboxcmdlet to update the SharePointURL property. We suggest that you don’t restore SharePoint to a new forest.

Kristin is a content strategist at Techarex Networks. Kristin follows the B2B technology space closely and loves to write on the latest changes in technology, futuretech and fixes for day to day how to issues. Besides writing Kristin also loves music, moves and skating.

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