Sometimes you need to grant a user access to another Office 365 mailbox. This is standard practice for shared mailboxes.
You may also need to delegate access to regular user mailboxes, e.g. if a secretary should manage a manager’s mailbox.
In Office 365, there are three types of delegation on a regular user mailbox:
- Send As
- Send on Behalf
- Full Access
This post will show you how to perform the delegation using the PowerShell command Add-MailboxPermission.
You’ll also see how to do it via the Exchange Admin Center and via the standard AD Users & Computers management console.
Mailbox Delegation Using PowerShell
Connect-ExchangeOnline
Add-MailboxPermission tycho.brahe@observatory.dk -User ole.roemer@observatory.dk -AccessRights FullAccess
- Start by establishing a connection with Exchange Online (lines 1).
- Delegate access to the mailbox using the Add-MailboxPermission command (line 2).
To review your change, use Get-MailboxPermission. The output may look similar to this:
PS C:\Windows\system32> Get-MailboxPermission tycho.brahe@observatory.onmicrosoft.com | ft User,AccessRights,IsInherited,Deny User AccessRights IsInherited Deny ---- ------------ ----------- ---- NT AUTHORITY\SELF {FullAccess, ReadPermission} False False niels.bohr@observatory.onmicrosoft.com {FullAccess} False False EURP189\Administrator {FullAccess} True True EURP189\Domain Admins {FullAccess} True True EURP189\Enterprise Admins {FullAccess} True True EURP189\Organization Management {FullAccess} True True EURP189\AM5P18901MB0148$ {FullAccess} True True NT AUTHORITY\SYSTEM {FullAccess} True False NT AUTHORITY\NETWORK SERVICE {ReadPermission} True False EURP189\Administrator {FullAccess, DeleteItem, ReadPermission, ChangePermission, ChangeOwner} True False EURP189\Domain Admins {FullAccess, DeleteItem, ReadPermission, ChangePermission, ChangeOwner} True False EURP189\Enterprise Admins {FullAccess, DeleteItem, ReadPermission, ChangePermission, ChangeOwner} True False EURP189\Organization Management {FullAccess, DeleteItem, ReadPermission, ChangePermission, ChangeOwner} True False EURP189\Public Folder Management {ReadPermission} True False EURP189\Exchange Servers {FullAccess, ReadPermission} True False EURP189\Exchange Trusted Subsystem {FullAccess, DeleteItem, ReadPermission, ChangePermission, ChangeOwner} True False EURP189\Managed Availability Servers {ReadPermission} True False EURP189\AM5P18901MB0148$ {FullAccess, DeleteItem, ReadPermission, ChangePermission, ChangeOwner} True False S-1-5-21-1589316702-2032257147-3807288276-5106 {ReadPermission} True False PRDTSB01\JitUsers {ReadPermission} True False
Notice that there are a lot of default permissions.
You can clean up your output by using some filtering:
PS C:\Windows\system32> Get-MailboxPermission tycho.brahe@observatory.onmicrosoft.com | ? {$_.User -like 'ole.roemer*'} | ft User,AccessRights,IsInherited,Deny User AccessRights IsInherited Deny ---- ------------ ----------- ---- ole.roemer@observatory.onmicrosoft.com {FullAccess} False False
Mailbox Delegation Using Active Directory Users & Computers
A more convenient option is to perform the mailbox delegation using the Active Directory Users & Computers management console.
You need to have the Easy365Manager snapin installed to follow this procedure. You can download a free, fully-functional 30-day trial here.
Open up user properties and go to the Mailbox tab. Click on Mailbox Delegation. Then add the delegatees to the selected type of delegation:

Delegating Mailbox Access Using Exchange Admin Center
You can also delegate mailbox access using the Exchange Admin Center. Follow the below steps to delegate permissions to a mailbox.
Open up the Exchange Admin Center using your admin account and locate the mailbox you want to delegate access to:

Open up mailbox properties and select Mailbox Delegation:

Select what type of access you want to delegate and add the delegates.
Summary
We’ve been looking at delegating mailbox permissions using PowerShell, AD Users & Computers (with the Easy365Manager snap-in), and Exchange Admin Center.
With Easy365Manager you can
- Manage all mail attributes and mailbox delegation in AD Users & Computers
- Manage Office 365 licenses and Office 365 mailboxes in AD Users & Computers
- Remove your on-premises Exchange Server
For the most common questions regarding installation, licensing and security read our FAQ.
For a complete list of features look here.