How to Update OWA Signatures with PowerShell

OWA stores user signatures in mailboxes, which makes it a lot easier for Office 365 admins to update signatures centrally with just a few lines of PowerShell and some HTML magic. OK, maybe more than a few lines… but it’s a lot less complicated than it is to mess around with the system registry and points the way to how Microsoft might introduce cloud signatures for all Outlook clients.