Give one user access to everyone else’s calendar in Office 365

Pretty easy! First connect your powershell to exchange as described here

Then run this:

Foreach ($mbx in get-mailbox){

$calendar=$mbx.alias+":\Calendar"

Add-mailboxfolderpermission -identity $calendar -user USERNAME -AccessRights PERMISSION

}

• USERNAME is the name of the user that you want to give the permissions to
• PERMISSION is the permission level (role) you want to give that user. The options are:
  • Author   CreateItems, DeleteOwnedItems, EditOwnedItems, FolderVisible, ReadItems
  • Contributor   CreateItems, FolderVisible
  • Editor   CreateItems, DeleteAllItems, DeleteOwnedItems, EditAllItems, EditOwnedItems, FolderVisible, ReadItems
  • None   FolderVisible
  • NonEditingAuthor   CreateItems, FolderVisible, ReadItems
  • Owner   CreateItems, CreateSubfolders, DeleteAllItems, DeleteOwnedItems, EditAllItems, EditOwnedItems, FolderContact,FolderOwner, FolderVisible, ReadItems
  • PublishingEditor   CreateItems, CreateSubfolders, DeleteAllItems, DeleteOwnedItems, EditAllItems, EditOwnedItems, FolderVisible,ReadItems
  • PublishingAuthor   CreateItems, CreateSubfolders, DeleteOwnedItems, EditOwnedItems, FolderVisible, ReadItems
  • Reviewer   FolderVisible, ReadItems

Hit enter and let ‘er rip.

NOTE: If permissions for this user have already been defined, this cmdlet will not replace those pre-existing permissions.