Create Shared Mailbox:
New-Mailbox -Shared -Name "User1" -DisplayName "User1" -Alias "User1"Set Mailbox Regional Config:
Set-MailboxRegionalConfiguration -Identity "User1" -Language nl-nl -LocalizeDefaultFolderName -TimeZone "W. Europe Standard Time"
Change Default permissions:
Set-MailboxFolderPermission -Identity User1:\Agenda -User Default -AccessRights PublishingEditor