What is Mailbox Delegation in Microsoft 365?

Mailbox Delegation in Microsoft 365 allows a user to grant access to their mailbox to another user. This feature enables shared management of emails, calendars, and other mailbox functions, ensuring seamless collaboration without sharing credentials.

Types of Mailbox Delegation

• Full Access:
  • Delegates can access and manage the entire mailbox, including reading, deleting, and creating items.
  • Does not include the ability to send emails as the mailbox owner.
• Send As:
  • Delegates can send emails that appear as though they are sent by the mailbox owner.
• Send on Behalf:
  • Delegates can send emails on behalf of the mailbox owner, with the sender’s name displayed as: “John Doe on behalf of Jane Smith.”

How to Set Up Mailbox Delegation

Mailbox delegation can be configured via the Microsoft 365 Admin Center or PowerShell. Example PowerShell command:

Add-MailboxPermission -Identity "Jane Smith" -User "John Doe" -AccessRights FullAccess

For Send As or Send on Behalf, use the Add-RecipientPermission cmdlet.

Use Cases for Mailbox Delegation

• Executive Assistants: Manage a manager’s emails and calendar
• Team Mailboxes: Allow multiple users to handle incoming emails.
• Helpdesk or Support Accounts: Shared access for teams to respond to customer queries.

Best Practices

• Regular Monitoring: Avoid over-privileging users to maintain security
• Monitor Delegated Access: Regularly review and audit permissions.
• Use Shared Mailboxes When Possible: For group collaboration, shared mailboxes are often a better fit.

Mailbox delegation streamlines collaboration and improves productivity while maintaining security and access control.

Explore More

• Using Add-MailboxPermission to provide Full Access Mailbox Delegation
• Using Add-RecipientPermission to provide Send As or Send on Behalf Mailbox Delegation