Sharing of data is done in a several ways and Office 365 by Microsoft does it in two ways. Folder sharing and providing Delegate Access are the two methods using which one can share data on Office 365 based platform. While folder sharing enables users to access the folder(s) of other users, delegate access is entirely different. In folder sharing one is provided access to your folder, but just access and not the right to act on your behalf to any of the email messages or meeting requests placed by anyone. Meanwhile, delegate access offers both as per the user requirement, i.e. you can share the access rights as well as the permissions to respond to emails / meetings on your behalf to another user. The latter is more of a feature that shares rights to your mailbox with other users and not just the data in it. The other user acts as an alternate account holder of your profile while you are unavailable. The following segment shares information on delegate access and workarounds for Office 365 mailbox delegation not working.

How To Assign Office 365 Mailbox Delegation

When you are not just handling your own account but another person’s as well, then it is better to add it to your account itself for easier access and manageability. However, in order to be able to do so, it is necessary for the owner of the mailbox to grant you permissions for handling the account mailbox. For this the manager, i.e. the owner of the mailbox must assign you with Folder Visible permission on Exchange mailbox’s root folder.

  1. Right click on the Exchange mailbox root folder and choose Folder Permissions from the given options.

  2. Click on the name of the user you want to assign as your delegate.

  3. From the Permissions given under ‘Other’ select the checkbox for ‘Folder Visible’

  4. Now click on Ok to assign the permission by enabling the changes made.

Workarounds for Making Delegate Access Work

Following are some of the workarounds that you can apply in the attempt of making delegate access to mailbox work.

  1. If the user is only able to view the mailbox data and not act on the delegated mailbox user’s behalf then:

    1. You need to assign Full Access Permission to the user mailbox

    2. In order to do so, using Windows PowerShell in connection to Office 365

    3. Type in the command given below and allow complete access to the user mailbox of your choice.


  1. If you are unable to send emails on behalf of the mailbox user then:

    1. Log into the Exchange admin center as Admin

    2. Click on Recipients followed by shared and double click on the DISPLAY NAME

    3. Then click on Mailbox Delegation to add the user of your choice in Send As

NOTE: Full Access Permission enables user to access the shared mailbox as the owner meanwhile the Send As permission enables them to act as the user and send emails on their behalf. In case the issue persists despite assigning Send As rights, create a shared mailbox, assign both the permissions, i.e. Full Access and Send As, and check the output received.

  1. In case of a miscellaneous issue:

    1. If there is an issue with the mailbox and you don’t know what it is the first step is to confirm the settings

    2. Check which mailboxes are assigned with mailbox delegate access

    3. Moreover, what permissions are assigned to which user

    4. The permissions are correctly assigned or not

    5. If not, then the problem is with Outlook

    6. Performing a reconfiguration of the profile or its repair would be a step probable to work in this case.

Office 365 is a hosted service and the origination of such issues could all the complicate the scenario. Therefore, it is suggested to use the first two methods before jumping on to profile reconfiguration if Office 365 Mailbox delegation not working.  If the requirement persist for accessing your old mailboxes by other or in any case if you do not want to assign permission of your mailbox just for the sake to check your old mailboxes only then you should take backup of Office 365 mailbox locally & then share your data to custodians. As a final solution, get in touch with an expert or the technical support for better assistance.