User Mailboxes
Manage Exchange Online user mailboxes. View mailbox properties, configure permissions, set up forwarding, manage delegates, and perform mailbox-level operations.
Mailbox List
The mailbox table displays:
| Column | Description |
|---|---|
| Display Name | User’s full name |
| Email Address | Primary SMTP address |
| Mailbox Type | User, Shared, Room, Equipment |
| Size | Current mailbox usage (GB) |
| Quota | Storage limit based on license |
| Items | Total item count |
| Archive | Archive mailbox enabled/disabled |
| Litigation Hold | Legal hold status |
| Last Activity | Last mailbox access date |
Mailbox Detail View
Click a mailbox to access detailed settings:
General Properties
- Primary and alias email addresses
- Display name and simple display name
- Custom attributes (1-15)
- Hide from Global Address List option
Mailbox Usage
- Current size and item count
- Deleted items size
- Quota warnings and limits
- Archive mailbox statistics
- Usage trend chart (30 days)
Email Addresses
- Primary SMTP address
- Additional aliases
- Add/remove email addresses
- Set new primary address
Mail Flow Settings
- Email forwarding (internal/external)
- Delivery options (send on behalf)
- Message size limits
- Recipient limits per message
Mailbox Permissions
- Full Access — Can open and manage entire mailbox
- Send As — Can send email appearing as mailbox owner
- Send on Behalf — Sends with “on behalf of” notation
- Folder-level permissions
Delegation
- Calendar delegates with permission levels
- Inbox rules created by delegates
- Folder sharing settings
Automatic Replies (OOF)
- View current OOF status
- Internal and external messages
- Scheduled time range
- Enable/disable OOF remotely
Quick Actions
- Convert to Shared — Convert user mailbox to shared mailbox (reclaim license)
- Enable Archive — Enable in-place archive for mailbox
- Set Forwarding — Configure email forwarding address
- Add Permissions — Grant access to another user
- Enable Litigation Hold — Place mailbox on legal hold
- Set Out of Office — Configure automatic replies
- Export to PST — Initiate mailbox export (eDiscovery required)
Mailbox Quotas
Default quotas based on license type:
| License | Mailbox | Archive |
|---|---|---|
| Exchange Online Plan 1 | 50 GB | 50 GB |
| Exchange Online Plan 2 | 100 GB | Unlimited* |
| Microsoft 365 E3 | 100 GB | Unlimited* |
| Microsoft 365 E5 | 100 GB | Unlimited* |
*Unlimited archive auto-expands in 50 GB increments up to 1.5 TB
Email Address Policies
Email addresses are typically generated by email address policies based on user attributes. Default format is usually firstname.lastname@domain.com. Additional aliases can be added manually.
API Reference
GET /api/email-and-collab/exchange/mailboxes
List all user mailboxes with statistics
GET /api/email-and-collab/exchange/mailboxes/:mailboxId
Get mailbox details and settings
PUT /api/email-and-collab/exchange/mailboxes/:mailboxId
Update mailbox settings
POST /api/email-and-collab/exchange/mailboxes/:mailboxId/permissions
Add mailbox permissions
POST /api/email-and-collab/exchange/mailboxes/:mailboxId/convert
Convert to shared mailbox
Exchange PowerShell Reference
Get-Mailbox -ResultSize Unlimited
Get-MailboxStatistics -Identity user@domain.com
Set-Mailbox -Identity user@domain.com -ForwardingAddress fwd@domain.com
Add-MailboxPermission -Identity shared@domain.com -User user@domain.com -AccessRights FullAccess