"Site mailbox couldn't be provisioned" error when you add a site mailbox to a SharePoint Online site


Consider the following scenarios:

  • Scenario 1: When you add a Site Mailbox app to a SharePoint Online subsite, you receive the following error message: 

    The site mailbox couldn't be provisioned.

    The Site Mailbox app hasn't been installed on the SharePoint site <URL for site>.

  • Scenario 2: When you add a Site Mailbox app to a SharePoint Online site collection, you receive the following error:
    The site mailbox couldn't be provisioned.

    SharePoint site <URL for site> couldn't be contacted because of the following the error: "WebException - Status:ProtocolError; Message: The remote server returned an error: (404) Not Found
Note In these error messages, <URL for site> represents the actual URL name of the site on which you experience the problem. 


Use one of the following methods, as appropriate for your situation.

Solution for scenario 1

To remove the ampersand (&) from the URL name for the subsite, follow these steps:

  1. Browse to the subsite on which the issue exists.
  2. Click the gear icon for the Settings menu, and then click Site settings.
  3. In the Look and Feel section, click Title, description, and logo.
  4. In the Web Site Address section, remove the ampersand (&) from the URL name field, and then click OK.
  5. Return to the site mailbox.

Solution for scenario 2

Create the site mailbox on a site collection whose URL doesn’t contains an ampersand (&). A site collection name that contains an ampersand in the URL does not support a site mailbox for that site.


This problem occurs when an ampersand (&) exists in the URL for either the subsite or the site collection.

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Article ID: 3179180 - Last Review: Dec 29, 2016 - Revision: 1