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Site mailboxes have been used by many organizations as their collaboration tool of choice. It came with a common mailbox to help you coordinate and store team or project related email in one place and a SharePoint site to store all your common files. However, as the way people collaborated has changed over the years, customers have asked for a solution that promotes a more active form of collaboration. Therefore, we have deprecated site mailboxes and encourage you to move to Office 365 Groups which provide a much richer collaboration experience.

For more information about that decision please see Deprecation of Site Mailboxes.

Groups in Office 365 let you choose a set of people that you wish to collaborate with and easily set up a collection of resources for those people to share. You don’t have to worry about manually assigning permissions to all those resources because adding members to the group automatically gives them the permissions they need to the tools your group provides.

Office 365 Groups go beyond what site mailboxes offer and include:

  • Guest access – With site mailboxes you couldn’t provide people outside your organization access. With groups you can offer guests access to email conversations, files and even the shared OneNote notebook.

  • Shared inbox - Where the conversations you traditionally have in the mailbox take place. This shared inbox is fully searchable so it creates a living archive of the group's messages. Newcomers to the group can search or scroll back through the history to get up to speed quickly on what's been communicated with the group previously.

  • Shared files library - Your group has a SharePoint files library where your users can store, share and collaborate on documents, workbooks, presentations, images or any other kind of file they need to work on.

  • Shared calendar - Your group gets a shared calendar to post events related to the group. Each member who has subscribed to the group is automatically invited to events posted to the calendar so those events can also appear on their Office 365 calendars if they wish.

  • Shared OneNote notebook - The group automatically has a shared OneNote notebook where group members can collect and collaborate on information. Many groups use the notebook to create a living wiki with frequently asked questions and other resources.

  • Content is discoverable - Groups in Outlook are public within your organization by default, which means that they are easy for other people in your organization to discover and join or review the materials in the group. If the content of the group is more sensitive you can switch the group to private, which hides the contents from non-members and requires the group owner to approve any requests to join.

  • Self-Service creation - Admins don't have to get bogged down by requests from users to create groups. Users can create their own groups as needed. If you want to control which users in your organization can create groups see Control who can create Office 365 Groups.

Directory Management

Keeping your directory under control is a concern of every administrator. Here are some of the tools Office 365 Groups offer to help make that easier:

  • Naming policies - Naming policies allow you to define what are, and are not, acceptable names for your groups. That prevents users from giving profane or prohibited names to groups. Additionally, you can enforce company standard prefixes or suffixes to the group names.

  • Dynamic membership - Dynamic membership allows you to set group membership by rule, which adds (or removes) group members based on metadata (such as department or role) in your active directory.

  • Hidden group membership - If you have a reason to want the membership list of your group to be confidential, for example if the members are students, you can hide the member list from outside parties.

  • Creation permissions - There may be some people in your organization that you don't want to be able to create new groups. There are several techniques for managing creation permissions in your directory.

  • Audit logs - You can have more confidence allowing your users to create groups and manage group membership because Office 365 Groups audit logs let you track down who created or deleted a particular group or made changes to the membership of the group.

Delivery Management

Delivery management gives you some methods to handle how messages should be sent or received by the group. Additionally, there are tools to monitor the flow of those messages.

  • Send as or Send on Behalf of - These settings allow specified users to send emails as if they came from, or are on behalf of, the group.

  • Sender restrictions - These settings allow you to control who is allowed to send messages to the group. The group can be configured to allow email from outside parties, but you may want to restrict that to only specific outside parties.

  • External user support - By inviting guests to your group you can choose to have them included in the email conversations in the group.

  • Transport rules - Transport rules work for groups just as they do for Exchange. The rules can look for messages that meet specific conditions and can then act on those messages.

  • MailTips - MailTips are informative messages displayed to users while they're composing a message. They can help reduce NDRs by warning a user if their message is likely to go to outside parties, or exceed message quotas.

  • Multiple proxy addresses - A group can have aliases just like a user mailbox does. Additional proxy addresses can be handy for accepting messages sent to those other aliases or for making it easier to reach a group that has a long or hard to spell name.

  • Max Send/Receive size - These quotas can help reduce issues with the group receiving (or sending) extremely large messages in order to better manage storage and bandwidth requirements.

Content Policies

Office 365 also gives you some tools to manage the kind of content that gets shared in your group.

Usage guidelines - You’ll be able to define usage guidelines for Office 365 Groups—to educate your users about best practices that help keep their groups effective and educate them on internal content policies.

Data classification - You’ll be able to create a customizable data classification system for Office 365 Groups that allows separation of groups by policy type (e.g., “unclassified,” “corporate confidential” or “top secret”). In this manner, your groups can exhibit the policies of other content in your organization. Extensible policy allows your organization to configure an endpoint that is called whenever a group is created or changed—and you can then implement your own policies for group creation or change.

Why are we making this change?

Site mailboxes encouraged a passive form of collaboration. With collaboration becoming more critical for modern teams, our customers have increasingly been asking for solutions that provide a more active collaboration experience. Therefore, we have decided to retire site mailboxes and promote the usage of groups.

Getting started with groups is easy and you can be up and running in minutes.

Create a SharePoint Online team site which comes with an Office 365 Group by following these steps:

  1. Go to SharePoint Online. You can get there by signing into your Office 365 portal at then clicking the App Launcher in the top right corner of your browser.

  2. Click on +Create Site on the SharePoint home page and choose Team Site

  3. Enter the new team site name, and description, in the pane that pops up. Fill in any other fields your organization requires and click Next.

  4. Add owners and members to the site in the following pane and click Finish. You may choose to add the same members that belonged to your classic experience team site.

The newly created SharePoint Online team site is now ready to use. See Create a team site in SharePoint Online for more details.

To access your groups, click the app launcher and go to Mail. You will find a Groups tab under Folders and a group will be created for you with the same name as the site name on SharePoint. This group houses the shared mailbox in the form of a Conversation space, the Files tab which gives a quick view of the Documents page from the SharePoint site, a group Calendar and a Notebook which can also be viewed from the SharePoint site.

You are now ready to use the group.

What about my existing Site Mailboxes?

We understand that some of you might have critical data in your site mailboxes which you will need for continuity of your operations. Your existing site mailboxes will continue to operate as before for the time being.

What if I'm using Project Online?

If you are a Project Online customer you will not be able to connect to the SharePoint Online team site. However, you can continue to use the classic experience project team site which will continue to work, minus the ability to create a new site mailbox. If you need a mailing solution along with the site, we recommend you to create a new Office 365 Group and use that for email. See Create a group in Outlook for more details.

We are in the process of working on a long-term solution and will notify you once we have a resolution.

What's Next?

We have started to roll out tenant admin tools to connect existing SharePoint team sites to new Office 365 Groups. For more information see this post.

More information

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This article was last updated on July 10th, 2018 as a result of your comments. If you found this information helpful, and especially if you didn't, please use the feedback controls below to let us know how we can make it better.

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