AB-900 lesson 2: where your data lives

In Microsoft 365, mail lives in Exchange Online mailboxes, shared documents live in SharePoint sites, personal files live in OneDrive, and Teams is a front end that stores its content in those same places: channel files in a SharePoint site, chat files in OneDrive, and compliance copies of messages in mailboxes. Knowing this map explains most “where do I configure it” questions, and later helps with retention, search and oversharing.

Exchange: mailboxes and groups

The Exchange admin center manages recipients. A user mailbox belongs to one licensed person. A shared mailbox lets several people read and send as one address, such as a support inbox. Room and equipment mailboxes represent bookable resources. A distribution group only forwards messages to its members; it has no inbox of its own and cannot be used for permissions or licences. A mail-enabled security group does both: it delivers mail and can also be used to grant access. Mail flow rules and connectors are managed here as well.

SharePoint: sites, libraries and folders

The figure above summarises the flow. In the SharePoint admin center an admin manages sites, tenant sharing settings and storage. Inside a site sit document libraries, and inside libraries sit folders and files. Permissions flow downward: folders inherit from the library, and the library from the site, unless inheritance has been broken for a specific item.

Two kinds of site matter. A team site is connected to a Microsoft 365 group, so membership of the group is membership of the site. A communication site is for broadcasting to many readers and uses the SharePoint permission groups directly. Private and shared channels in Teams each get their own separate site.

Site roles

For a team site connected to a Microsoft 365 group or a Teams team, group owners become site owners and group members become site members, and the recommended place to manage this is the group or the team, not the site. A sharing link for one file gives that person access to that item only, without making them a site member.

Teams: teams, channels and policies

The Teams admin center manages teams, channels and policies. A team is backed by a Microsoft 365 group. Standard channels are visible to all team members, private channels to selected members, and shared channels can include people from outside the team or organisation. Policies (messaging, meeting, app setup) are assigned to users or groups and decide what features those people get; they do not live inside a team.

OneDrive

OneDrive is each person’s own file space. Admins manage it from the SharePoint admin center, because OneDrive is built on the same platform. Files in OneDrive are private until the owner shares them.

Where Teams content is stored

Teams stores content in the services above:

• Channel files go to the document library of the team’s SharePoint site, in a folder named after the channel.
• Files shared in one-to-one and group chats are stored in OneDrive and shared from there.
• Chat messages: the Teams chat service holds the primary copy, and a copy for compliance is kept in a hidden folder in the mailbox of each person in the chat.
• Channel messages: a similar hidden folder in a group mailbox of the team holds the compliance copy.

This is why eDiscovery and retention for Teams involve Exchange, SharePoint and OneDrive together.

Worked example: a 120-person firm sets up a project

A 120-person consultancy starts a project with an outside partner. The admin creates a team, which also creates a Microsoft 365 group and a SharePoint site. The project lead becomes an owner, colleagues become members. A contractor needs read-only access to the final reports only, so the admin does not add them to the team; the contractor receives a Visitors-level role on a separate reports site. The project mailbox for incoming requests is created as a shared mailbox in the Exchange admin center, so three people can answer from one address without extra licences. When the partner joins a sensitive channel, the admin picks a shared channel so the partner works in that channel only. Each choice maps to one workload and one admin center.

Easy to confuse

Key points

• Exchange holds mailboxes and groups; SharePoint holds sites, libraries and folders; OneDrive holds personal files.
• Teams does not store files itself: channel files go to SharePoint, chat files to OneDrive.
• Teams chat and channel messages have compliance copies in Exchange mailboxes.
• Site roles are Owners (full control), Members (edit) and Visitors (read).
• Teams policies are assigned to users or groups, not stored in a team.

Check yourself

This lesson continues domain one of the course, which carries 30 to 35% of the exam. The recap page Microsoft 365 core features explained covers the same objects in table form, and the cheat sheet keeps the admin center map within reach.