2.1.2. Exchange Online Admin Center: Mailboxes and Mail Flow
š” First Principle: Exchange Online is the email service underlying M365, and its admin center manages the objects that make email work ā mailboxes (where mail lives), distribution lists (who gets CC'd on group emails), and mail flow rules (what happens to a message in transit).
Every licensed M365 user with an Exchange Online plan automatically gets a mailbox provisioned. But beyond the basic user mailbox, Exchange Online has several specialized mailbox types:
| Mailbox Type | Purpose | License Required |
|---|---|---|
| User mailbox | Individual user's email | Yes |
| Shared mailbox | Accessed by multiple users (e.g., info@company.com) | No (users need Exchange license) |
| Room mailbox | Bookable conference room resource | No |
| Equipment mailbox | Bookable resource (e.g., company car) | No |
| Distribution list | Group email address ā delivers to all members | No |
| Microsoft 365 Group | Shared mailbox + calendar + SharePoint + Teams | Yes (for members) |
Mail flow rules (also called transport rules) intercept messages in transit and apply actions: add disclaimers, redirect messages, block certain content, encrypt based on conditions. These are configured in the Exchange admin center.
ā ļø Exam Trap: Anti-spam, anti-phishing, safe links, and safe attachments are not configured in the Exchange admin center. Those are email security policies managed in the Microsoft Defender portal. Exchange admin center = mailbox objects and mail flow. Defender = email threat protection.
Reflection Question: Your organization wants all outbound emails to include a legal disclaimer at the bottom. Which feature and which admin center do you use?
