$UserCredential = Get-Credential

$Session = New-PSSession -ConfigurationName Microsoft.Exchange -ConnectionUri https://outlook.office365.com/powershell-liveid/ -Credential $UserCredential -Authentication Basic -AllowRedirection

Import-PSSession $Session -DisableNameChecking

Add-MailboxFolderPermission -Identity <user1@domain.com>:\Calendar -User <user2@domain.com> -AccessRights Editor -SharingPermissionFlags Delegate