Skype for Business Hybrid with On-Premise PSTN.

As you may be aware, are PSTN Calling only available in US, UK, Puerto Rico, Spain and France (October 2016).

In this post I will try to explain how to move a user from On-Prem to Skype Online, and still use On-Prem PSTN.

Start Windows power shell as administrator

1.Import-Module skypeonlineconnector

2.$cred = Get-Credential
3.$Session = New-CsOnlineSession -Credential $cred -Verbose
4.Import-PSSession $session

Yes you can create a script to make it easier. Save the text below in a ps1 file and then run.

Import-Module SkypeOnlineConnector
$session = New-CsOnlineSession -Credential $credential
Import-PSSession $session
Get-CsTenant | fl DisplayName

First you need to create a VoiceRoutingPolicy

New-CsVoiceRoutingPolicy -Identity "HybridVoiceRoutingPolicy" -Name "HybridVoiceRoutingPolicy" -PstnUsages "Long Distance"

If you have multiple usage, with multiple SIP Trunk, you need to add the policy like this

Set-CsVoiceRoutingPolicy -Identity "HybridVoiceRoutingPolicy" -PstnUsages  "SW - Sweden", "BU - Bulgaria", "DE - Germany", "DK - Denmark", "FI - Finland", "LV - Latvia", "UK - England", "US - USA"  ,"Long Distance"

Then you need to grant this policy to users thats need to be moved to Skype Online

Grant-CsVoiceRoutingPolicy -Identity user@company.com -PolicyName HybridVoiceRoutingPolicy

Enable the Skype for Business Cloud PBX before you move the user to Skype Online

Run then a directory sync between local AD and Azure AS

The user must be enabled for enterprise voice with Line URI, Dial-plan and Voice Routing before you move the use.

Then it is ready to move the user from On-Prem to Skype Online.

If you run Get-CsOnlineUser -Identity user@company.com | fl *voice*, *line*, *dial* you will see that HostedVoiceMail and EnterpriseVoice is False.

Set-CsUser -Identity user@company.com -EnterpriseVoiceEnabled $true

Set-CsUser -Identity user@company.com -HostedVoiceMail $true

You will see the EV users in the O365 portal like this



In Skype On-Prem Control panel will the user look like this.

Configure Skype Hybrid from Skype Online to Skype On-Prem

I know this is like swearing in church ... However, due to limited functionality in Skype Online as Persistent Chat, Enterprise Voice functionality, Common Area, Response Group, or that you want to have full control over your Skype environment, you want to set up Skype On-Prem.


Microsoft has documented very well how to configure Skype Hybrid by going from Skype On-Prem to Skype Online. But how to configure this in the other direction is not as well documented.


What if you have a customer running Skype Online already and want to use Skype On-Prem?
Yes, you start configuring Skype Hybrid in the usual way with ADFS Sync, DirSync, Federation with O365, Shared SIP address space etc.


Once you have set up Skype Hybrid, you expect to be able to see your Skype Online users Skype Control Panel?


Skype Online has not the same as function as Exchange Hybrid, which can write attributes back. Therefore, we first need to run an export of Skype Online users to csv file. Then we need to enable these users to Skype On-Prem.

I've created a script that retrieves users from Skype Online and puts them in a CSV file

Then start Skype On-Prem power shell and run a Enable-CsUser with parameter -HostingProviderProxyFQDN = sipfed.online.lync.com

After you run the import scripts, then Skype Online users be visible in Skype On-Prem Control Panel. You will now be able to move the users between Skype Online and Skype On-Prem

Allow anonymous participants to dial out

Be carefull if you decide to enable "Allow anonymous participant to dial out" from Skype conference

If you enable this feature, you can experience anonymous users, using your Skype for Business solution to call to countries where it is expensive to call like countrys below.

•         Saint Lucia (+1758)
•         Saint Vincent and the Grenadines (+1784)
•         Cayman Islands (+1345)
•         Grenada (+1473)
•         Dominica (+1767)
•         Turks and Caicos Islands (+1649)


The scenario below can become reality if you have this feature on. It could cost your company a lot of money!


If you know an old URL for a Skype Meeting you can copy/paste the URL in the browser. At the end of the URL you add ?sl=1 to force starting the Skype Web App

Type any name you want and then hit the green button



Click on the partisipants symbol. See red arrow

You can then enter any PSTN number in the world, and then click Call. (The SIP trunk, Dial-plan etc must allow calls to the country)

Who should pay for this call? Yes, you are right, your company! It quickly becomes expensive for your company with this feature on.


You can find this information in Skype Monitoring reports - User Activity Report


1: The user who create the Skype Meeting

2: You will see the Anonymous user, who join the meeting from WepApp as anonymous@anonymous.invalid

3: The PSTN number the Anonymous user call from the conference

Conclusion: Don`t enable this feature!

Saving phone number disabled due to the server policy

Do you get this error when you log on Skype for Business on an iOS Device?

If yes, then you probeably have problems with "Call me back" feature? In certain scenarios, you may not want to use VoIP. This may be related to poor network where you do not have neither WiFi, 3G or 4G networks.
In these scenarios, you would like to be called back from the Skype server instead of dialing into itself whith entering dialin number and enter a long code.


With SfB version 6.5.0.177 on iOS, then you will get this warning when trying to save your own mobile number which is also stored in Active Directory.


If you remove the mobile number in Active Directory, you don`t get this warning and the Call me back Works.


This don`t happens with Windows Phone or Andriode!


Microsoft is trying to make a fix for this in the future

Skype for Business Cloud PBX - PSTN incoming calls failed when default SIP domain is different than users SIP address

When you deploy Cloud PBX with on-premise PSTN Connectivity there is possible for Skype Online users to call and receive calls through the local SIP Trunk.

I followed this article to configure this settings.

Outgoing calls works fine for Online users, but incoming calls from PSTN to Skype doesn`t work. After some investigation I notice the error "Unable to resolve DNS SRV record" on the SfB Mediation Server



Our Default SIP domain is internal.com, and we have added company.com as additionaly SIP domain. This has worked fine over severals years.




When I look in the log file on the Mediation Server, I see that Invite goes to +47xxxx@internal.com



I see this error in the log file. "Unable to resolve DNS SRV record"; domain="internal.com"

 We don`t have any SRV record for the internal domain and therefore this error.


I think the solution for this is to change the Default SIP Domain, but this will have huge inpact on your deployment.


I am in touch with Microsoft on this issue. A update will come as fast I solve this.


Update June 21th: It was as expected, the response from Microsoft is changing the default SIP domain so that it is equal to the Skype Online