Lync 2010 with Enterprise Voice attaches a phone number to a user with a direct one to one relationship. This means that when a user departs, the account should get disabled along with any Lync attachments. In turn, this abandons the phone number that was attached to the user. All great by design, but what about external people that are still calling the number of the departed user? You could leave the user’s Active Directory account disabled, leave Lync attached and configure it that way, but that’s a big hassle. Microsoft covers this scenario with a feature called “Unassigned Number”. Unassigned Number lets you configure an Announcement on an entire number range. The idea is that if any extension in the number range configured (which can be a single number) is called and isn’t attached to a user, it will divert the call to either an Announcement or an Exchange UM Auto Attendant number. Generally just the Announcement is fine, because the Announcement can be configured to be nothing, but divert the call to wherever you want it to go afterwards. The Announcement needs to be configured before you create an Unassigned Number Range, which can only be managed by PowerShell. The Unassigned Number Range can be created via the Lync Control Panel GUI or PowerShell which seems a bit inconsistent. Creating an Announcement is rather easy still, with a great guide from TechNet here. The important bits are to give your Announcement a name, tell it which Lync Pool to use and give it a target SIP address to send the call to. An example command do this is: New-CsAnnouncement -Identity ApplicationServer:lyncpool.mydomain.com -Name "Forward Announcement" -TargetUri sip:reception@mydomain.com Note that if you use a direct phone number for the sip address, you need to append...