Symptoms
Assume that you send a user a clickable link that's implemented by your enterprise through chat or instant message in Microsoft Lync 2013 (Skype for Business). When the user clicks it, the link is unavailable, and the user receives an error message that resembles the following:
"The web page <link> was not loaded in response to you clicking the link because it is either invalid or restricted for security reasons. For more information, contact your system administrator."
This issue occurs because, for security, only certain URL prefixes are permitted to be clickable in the Lync 2013 (Skype for Business) client.
Resolution
To enable additional URL prefixes to be clickable, a new feature is included in the November 1, 2016, update (KB3127934) for Lync 2013 (Skype for Business).
After you install the update, a new client policy entry named CustomSafeUrlPrefixes must be created and added to your client policies. The value of this client policy entry should be the list of URL prefixes which should be made clickable in your organization. Each URL prefix in the list should end with a colon, and no separator is allowed between URL prefixes listed. It's supported to add up to 20 additional URL prefixes.
For example, you can create a new policy entry to enable two additional clickable URL prefixes, and add it to the global client policy:
$a = New-CsClientPolicyEntry -Name CustomSafeUrlPrefixes -Value "myprotocol:someprotocol:"
Set-CsClientPolicy -PolicyEntry @{Add=$a}
Warning If the value of this client policy entry is configured incorrectly, it could cause the registration of all clickable URL prefixes to fail. This makes all links unclickable in the Lync 2013 (Skype for Business) client. All additions and changes to this client policy entry should be evaluated and tested carefully to make sure that it's working correctly.
Note Lync 2013 was upgraded to Skype for Business in April 2015.
