Configure Mailbox Permissions

Permissions tab

The Permissions tab is used to manage delegated mailbox access for the selected Exchange Online mailbox. This tab allows administrators to assign users who can send messages as the mailbox, send messages on behalf of the mailbox, open the mailbox with full access, or access mailbox calendar and contacts data.

This tab is important for shared responsibility scenarios, executive assistant workflows, shared mailbox management, team coverage, and controlled delegation. Permission changes should be reviewed carefully because they affect who can act on or access mailbox content.

Send as permission

The Send As Permission section controls which users can send messages as the selected mailbox.

1. Search allows the administrator to find and select a user who should receive Send As permission.
2. Add assigns Send As permission to the selected user.

When Send As permission is granted, the delegated user can send email that appears to come directly from the mailbox. This permission should be assigned only when the delegated user is allowed to represent the mailbox identity itself.

Send on behalf

The Send On Behalf section controls which users can send messages on behalf of the selected mailbox.

1. Search allows the administrator to find and select a user who should receive Send on Behalf permission.
2. Add assigns Send on Behalf permission to the selected user.

Send on Behalf permission is different from Send As. Messages sent with this permission usually indicate that one user sent the message on behalf of another mailbox. This is useful for assistants, delegates, or team members who need to send official communication while still showing delegated authorship.

Full access

The Full Access section controls which users can open and manage the mailbox content.

1. Search allows the administrator to find and select a user who should receive Full Access permission.
2. Add assigns Full Access permission to the selected user.

Full Access permission allows the delegated user to open the mailbox and work with its contents. This is commonly used for shared mailboxes, support mailboxes, manager-assistant workflows, or administrative recovery scenarios. It does not necessarily grant permission to send as the mailbox unless Send As or Send on Behalf permissions are also configured.

Calendar access

The Calendar Access section controls which users can access the mailbox calendar.

1. Search allows the administrator to find and select a user who should receive calendar access.
2. Add assigns calendar access to the selected user.

Calendar access is useful when assistants, managers, team members, or scheduling staff need visibility into the mailbox calendar. This can help with meeting coordination, room or resource scheduling, or user calendar management.

Contacts access

The Contacts Access section controls which users can access the mailbox contacts.

1. Search allows the administrator to find and select a user who should receive contacts access.
2. Add assigns contacts access to the selected user.

Contacts access is useful when another user needs to review or manage contact information stored in the mailbox. This should be assigned only when the delegated user has a real business need to access those contacts.

Permissions tab actions

1. Save Changes And Exit saves the permission changes and returns to the previous page.
2. Save Changes saves the permission changes without leaving the mailbox edit page.

Before saving changes on this tab, administrators should confirm that each permission type matches the intended access model. Send As, Send on Behalf, Full Access, Calendar Access, and Contacts Access serve different purposes and should not be assigned interchangeably.

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