What does the "Custom" option mean in Outlook calendar Sharing and Permissions?

Question

In Outlook/OWA, Calendar, Sharing and Permissions, it shows a list of individuals "Inside your organization", which each have options for different permissions. One option is "Custom". See screen shot below...

The only documentation I can find online re: this is: "Indicates that the user has custom access permissions on the folder." (see screen shot at bottom); But this doesn't EXPLAIN what those permissions are or how to set custom permissions.

Thank you in advance!

Answer 1

To put it simply, "custom" means that the permissions granted to the user do not not match the default 4 types (Can view free/busy, can vie titles and locations, can view all details, can edit). As any other mailbox folder, the Calendar folder supports granular delegation of permissions, as summarized for example in this article: https://learn.microsoft.com/en-us/powershell/module/exchange/add-mailboxfolderpermission?view=exchange-ps#-accessrights

The following individual permissions are available:

    None: The user has no access to view or interact with the folder or its contents.
    CreateItems: The user can create items within the specified folder.
    CreateSubfolders: The user can create subfolders in the specified folder.
    DeleteAllItems: The user can delete all items in the specified folder.
    DeleteOwnedItems: The user can only delete items that they created from the specified folder.
    EditAllItems: The user can edit all items in the specified folder.
    EditOwnedItems: The user can only edit items that they created in the specified folder.
    FolderContact: The user is the contact for the specified public folder.
    FolderOwner: The user is the owner of the specified folder. The user can view the folder, move the folder and create subfolders. The user can't read items, edit items, delete items or create items.
    FolderVisible: The user can view the specified folder, but can't read or edit items within the specified public folder.
    ReadItems: The user can read items within the specified folder.

The roles that are available, along with the permissions that they assign, are described in the following list:

    Author: CreateItems, DeleteOwnedItems, EditOwnedItems, FolderVisible, ReadItems
    Contributor: CreateItems, FolderVisible
    Editor: CreateItems, DeleteAllItems, DeleteOwnedItems, EditAllItems, EditOwnedItems, FolderVisible, ReadItems
    NonEditingAuthor: CreateItems, DeleteOwnedItems, FolderVisible, ReadItems
    Owner: CreateItems, CreateSubfolders, DeleteAllItems, DeleteOwnedItems, EditAllItems, EditOwnedItems, FolderContact, FolderOwner, FolderVisible, ReadItems
    PublishingAuthor: CreateItems, CreateSubfolders, DeleteOwnedItems, EditOwnedItems, FolderVisible, ReadItems
    PublishingEditor: CreateItems, CreateSubfolders, DeleteAllItems, DeleteOwnedItems, EditAllItems, EditOwnedItems, FolderVisible, ReadItems
    Reviewer: FolderVisible, ReadItems

The following roles apply specifically to calendar folders:

    AvailabilityOnly: View only availability data
    LimitedDetails: View availability data with subject and location

Microsoft decided to "simplify" the way permission are displayed in OWA/Outlook, thus you only see the 4 "most used" types nowadays. If you check the permissions via PowerShell though, the "custom" entry will be translated to one in the list above.

Answer 2

Hi @Simmomi

I agree with Vasil Michev. The Custom option in Outlook calendar sharing and permissions allows you to specify the level of access you want to grant to others who view your calendar.

But this doesn't EXPLAIN what those permissions are or how to set custom permissions.

To learn more about shared calendar permission settings, please refer to the following articles:

Calendar sharing in Microsoft 365 - Microsoft Support

Allow someone else to manage your mail and calendar - Microsoft Support

Hope this helps!

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