Exchange Online: Mailboxes & Distribution
Exchange Online is the engine behind Outlook. As an admin, you manage mailboxes, distribution lists, and mail flow — all from the Exchange admin center.
What is Exchange Online?
Exchange Online is the post office behind your Outlook.
When you send an email, Outlook is the letterbox you drop it into. But Exchange Online is the post office that actually sorts, delivers, and stores it. It also manages the address book (distribution lists), forwarding rules, and anti-spam filtering.
As an admin, you don’t usually touch Exchange unless you need to create a special mailbox (like info@company.com), set up a distribution list (all-staff@company.com), or troubleshoot delivery issues.
Core Exchange objects for the exam
Mailbox types
| Feature | When to Use | License Needed? | Example |
|---|---|---|---|
| User mailbox | Personal mailbox for an employee | Yes | maya@northwave.com |
| Shared mailbox | Team inbox — multiple people access it | No (up to 50 GB) | support@northwave.com |
| Resource mailbox (Room) | Bookable meeting room | No | board-room@northwave.com |
| Resource mailbox (Equipment) | Bookable equipment | No | projector-1@northwave.com |
Shared mailboxes — the exam favourite
Shared mailboxes are tested heavily because they’re a cost-efficient solution:
- No license required (up to 50 GB storage — beyond that, you need a license)
- Multiple people can send and receive from the same address
- Perfect for team inboxes: support@, info@, sales@, hr@
- Created in the Exchange admin center or M365 admin center
Exam tip: If a question says “the team needs a shared email address without buying extra licenses” → the answer is shared mailbox.
Distribution lists
Distribution lists let you send one email to many people at once:
| Type | Description | Membership | Example |
|---|---|---|---|
| Distribution group | Static list of members | Manually managed | all-marketing@northwave.com |
| Mail-enabled security group | Same as above + can be used for permissions | Manually managed | finance-team@northwave.com |
| Dynamic distribution group | Members auto-calculated from rules (e.g., “all users in Marketing department”) | Automatic based on attributes | all-sydney-staff@northwave.com |
Scenario: Maya sets up Northwave's email
Maya’s first week at Northwave, she needs to set up:
- Shared mailbox →
support@northwave.com— customer service team of 5 people shares this inbox - Room mailbox →
boardroom@northwave.com— people book it from their Outlook calendar - Distribution group →
all-staff@northwave.com— 500 employees, manually managed - Dynamic distribution group →
auckland-staff@northwave.com— auto-includes everyone where City = Auckland
All configured in the Exchange admin center → Recipients.
The Exchange admin center
Key areas Maya uses daily:
| Section | What’s There |
|---|---|
| Recipients → Mailboxes | User mailboxes — view, edit, manage |
| Recipients → Groups | Distribution lists and M365 Groups |
| Recipients → Resources | Room and equipment mailboxes |
| Recipients → Shared | Shared mailboxes |
| Mail flow → Rules | Transport rules (e.g., add disclaimer to outgoing email) |
| Mail flow → Accepted domains | Domains this Exchange org handles email for |
Key exam concept: The Exchange admin center manages email-specific objects. User accounts and licenses are managed in the M365 admin center. Security policies are managed in Entra. Don’t confuse the admin centers.
🎬 Video walkthrough
🎬 Video coming soon
Exchange Online Essentials — AB-900 Module 2
Exchange Online Essentials — AB-900 Module 2
~8 minFlashcards
Knowledge Check
Brew & Byte needs a shared email address (hello@brewandbyte.com) that Kai and Zoe can both access. They don't want to buy an extra license. What should they create?
Northwave wants to create an email list that automatically includes all employees in the Auckland office. When new staff join in Auckland, they should be added automatically. Which type should Maya create?
Next up: SharePoint — sites, libraries, permissions, and the admin center where it all comes together.