Beginning March 2017, new SharePoint Online organizations will no longer have access to the Site Mailbox feature, existing SharePoint Online organizations will no longer be able to create new Site Mailboxes; however, any Site Mailboxes provisioned prior to March 2017 will continue to function.
How does this affect me?
You are receiving this message because our reporting indicates your organization has one or more Site Mailboxes available. Beginning March 2017, your users may no longer create new Site Mailboxes.
In September 2017, we will have a process in place allowing you to transition your existing Site Mailbox site to an Office 365 Group. We will communicate again in June 2017, via Message Center, with more details.
What do I need to do to prepare for this change?
If you are using the Site Mailbox feature in SharePoint Online, you should consider transitioning to Office 365 Groups, to support email-centric collaborative scenarios.
Please click Additional Information to learn more.