Escalate CCE PSTN Call to Conference with Skype for Business Online

Working with PSTN Conferencing in your Office 365 Skype for Business Online Tenant.

ID PSTN -> SfBOnlUsr call

Start and instant (Impromptu) Meeting or schedule a Online Meeting as usual from Outlook or your Client App.  After the meeting is escalate into ConfCall, the MCU SfB OnLine Server will send reinvite to MediationServerHybrid.

This is illustrated in the drawings below.

First we have a look into the outbound call to a PSTN user:


Next, we have a look into the inbound call from a PSTN user:


Configure online hybrid Mediation Server Settings

The setup process is curial and needs to be follow as below:

When a P2P call is escalated to a PSTN conference, the Skype for Business Online conferencing server will send an invite to the Cloud Connector Mediation Server. To ensure that Office 365 can route this invite successfully, you need to configure a setting in your online tenant for each Cloud Connector Mediation Server as follows:
1. Create a user in the Office 365 admin portal. Use any user name you want, such as “MediationServer1.”
Use the default SIP domain of Cloud Connector (the first SIP domain in the .ini file) as the user domain.
Do not assign any Office 365 licenses (such as E5) to the account you create. Wait for Office 365 AD sync to complete.

2. Start a tenant remote PowerShell session using your tenant admin credentials, and then run the following cmdlet to set the Mediation Server and Edge Server FQDN to that user account, replacing <DisplayName> with the Display Name of the user for the account you created:

Copy Set-CsHybridMediationServer -Identity <DisplayName>
-Fqdn <MediationServerFQDN> -AccessProxyExternalFqdn <EdgeServerExternalFQDN>

3. For Identity, use the Display Name of the Office 365 user account you created for this Mediation Server.

MediationServerFQDN, use the internal FQDN defined for your Mediation Server.
EdgeServerExternalFQDN, use the external FQDN defined for Edge Server Access Proxy. If there are multiple Cloud Connector PSTN sites, choose the Edge Server Access Proxy FQDN assigned to the site where the Mediation Server is located.
4. If there are multiple Cloud Connector Mediation Servers (multiple-site, HA), please repeat the previous steps for each of them.

Further conference expansion with Dial-In and Dial-Out from/to PSTN:

If another User should be called into the conference the Microsoft Office 365 PSTN Conferencing Bridge breakout is used.

Dial-Out will be charged within your Office 365 Subscription.
If you have PSTN Calling activated, the outbound call with be deducted from your PSTN Calling minutes, or individually charged based on the Microsoft Destination minute pricings.

Other Users calling into the conference with PSTN, use the Dial-In Bridge in Office 365 Skype for Business.




  1. Hi,

    Trying to set the hybrid mediation server with Set-CsHybridMediationServer but I get "User not found".

    I created a user named MedServer01 in my tenant, only a cloud account.... then I run:
    Set-CsHybridMediationServer -Identity MedServer01 -Fqdn MedServer01.sfbccedom01.local -AccessProxyExternalFqdn

    Does the account need to be in on-prem AD also? Or what could be wrong you think?


    1. Hi Rob,
      no, this account is a native Online User. Important is, that this user has the correct SIP Domain for URI/ User Login. The replication within Azure AD might take up to 24 hrs. Usually it's much faster.
      In your case, the "MedServer01" is not a user account, you need to use the format ""

    2. Hey Thomas,

      just a quick question: did you successfully implement this?
      I ask for the following reason:
      According to Technet you should create a online User without any license and with the default sipdomain of the CCE installation. If i try this i receive the following errormessage in powershell.

      PS C:\Users\max> New-MsolUser -UserPrincipalName "" -DisplayName "medsrv1"
      New-MsolUser : You must provide a required property: Parameter name: FederatedUser.SourceAnchor
      At line:1 char:1
      + New-MsolUser -UserPrincipalName "" -DisplayName "medsrv1"
      + ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
      + CategoryInfo : OperationStopped: (:) [New-MsolUser], MicrosoftOnlineException
      + FullyQualifiedErrorId : Microsoft.Online.Administration.Automation.RequiredPropertyNotSetException,Microsoft.Onl

      so i decided to sync the user from onprem to the cloud and i can succesfully query that account!

      PS C:\Users\max> get-msoluser -UserPrincipalName

      UserPrincipalName DisplayName isLicensed
      ----------------- ----------- ---------- medsrv1 False

      so everything looks actually fine right ? Now if i wanna setup the HybridMediationServer for that account i receive the following error message.

      PS C:\Users\max> Set-CsHybridMediationServer -Identity "" -Fqdn medsrv1.cce_test.local -AccessProxyExternalFqdn
      User not found.
      + CategoryInfo : InvalidArgument: (:String) [Set-CsHybridMediationServer], ItemNotFoundException
      + FullyQualifiedErrorId : SessionStateException,Microsoft.Rtc.Management.AD.Cmdlets.SetHybridMediationServerCmdlet
      + PSComputerName :

      I encountered this issue already on 3 installation in different tenants without any chance to resolve it.

      Any help would be much appreciated.

    3. Hi it seem that you have an "_" in den DNS name. This isn't support in A Records. Only SRV Records are reserved for this. Could you try it without "_"/ underscore.


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