In-place online archive, this means having your online archive readily available in Outlook, is only available if you have Office ProPlus or a standalone version of Outlook. Outlook from Office Standard (including Office365 Business Premium) does not provide access to the online archive, and as such, it can only be opened from OWA.
If Outlook displays duplicate reminders for the same event, and you don't actually have two appointments with the same content, or the same PST/OST in your profile multiple, you probably have a corrupt reminder "folder", an internal hidden folder containing your reminders.
You can rebuild the reminder folder by exiting Outlook completely, then starting it with a parameter:
You can start Outlook with this parameter through the Run dialog (Start → Run, or WinKey + R).
From KB 2682333:
When your hyperlinks in your Outlook signature gets replaced by so-called "field codes", you may have inadvertedly pressed the magic key combo Alt+F9:
You can reverse the effect by pressing it again. This only works when the message field has focus.
To allow an Exchange user to send from an external e-mail address, perform the following steps:
Get-MailContact MyUser@MyExternalDomain.com | Add-ADPermission -User MyUser@MyLocalDomain -AccessRights ExtendedRight -ExtendedRights "Send As"Replace the first e-mail address with the external one, the second part contains the user you wish to assign the permission to.