Merge pull request MicrosoftDocs#4049 from martboe/patch-3

Update comment on UserPrincipalName

Author: kenwith

skype/skype-ps/skype/New-CsOnlineApplicationInstance.md

@@ -41,7 +41,7 @@ Call Queue: 11cd3e2e-fccb-42ad-ad00-878b93575e07
 ## PARAMETERS
 
 ### -UserPrincipalName
-The user principal name. It will be used as the SIP URI too.
+The user principal name. It will be used as the SIP URI too. The user principal name should have an online domain.
 
 ```yaml
 Type: System.String