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Managing SIP Identities in Skype for Business Online

As we prepare for the migration from on-premises Skype for Business to Skype for Business Online, there are a few important considerations to bear in mind before you take the leap. I will be covering these in a series of posts (hopefully), today I want to share with you a common scenario we will face while preparing for migration.

We are well aware of the pre-requisite for Office 365 that demands an Active Directory synchronised user must have a publically routable User Principal Name (UPN). So critical is this requirement that it is now engrained in every consultant’s mind and increasingly customers are becoming more aware of this without us even mentioning it. However, this can often produce its own unique challenges.

Many organisations set their users up with an ambiguous username, something that does not immediately identify a user by name e.g. a134g@domain.com rather than markv@domain.com. This is to avoid name conflicts and was often used as an additional domain security measure. When a user is synchronised to Office 365 their UPN is used to provision the identity and service addresses for Exchange and Skype for Business. Often the case is that users UPNs do not match their publically available contact information such as their e-mail address. E-mail addresses are usually more personable to each users and contain their true identity e.g markv@domain.com. In order to integrate Skype for Business Online with Exchange properly it is important that the user’s SIP address matches their primary e-mail address i.e. markv@domain.com and not a134g@domain.com.

However, when you perform an AD Sync with Office 365 the user’s Skype for Business Online identity is provisioned using the UPN like so:

On-premises Identity (UPN = a134g@domain.org)

Synchronised Identity in Office 365 Portal also a134g@domain.org

PowerShell output showing primary SIP Address in Skype for Business Online

In order to change this, the solution is to look and edit the on-premises identity, as this is the source of authority for this person’s cloud identity. Specifically, we need to modify an attribute on the user’s Active Directory account called msRTCSIP-PrimaryUserAddress. In order to find this attribute, your on-premises Active Directory domain is required to be prepared for Lync / Skype for Business On-premises. Therefore, you may need to download the on premises software and run AD schema preparation to have this property available. I say may read on.

First change find and change this attribute

Click on edit and enter the desired address in this format: sip:markv@domain.org

Perform directory synchronisation using AADSync and then check the SIP Address of the online identity. You should see that is has changed

Please note that this only works for synchronised identities. Cloud identities must be provisioned with the primary SIP address as the username.

If you have not prepared your Active Directory domain from on-premises Lync / Skype for Business and do not have the msRTCSIP-PriamryUserAddress attribute, there is an alternative method you can use. Instead we can use the ProxyAddresses attribute that is natively part of Active Directory. This attribute is the same on you use for provisioning e-mail addresses to get around the same issue as we have. Open the ProxyAddressess attribute and add a new Proxy Address into the list using the following format: sip:markv@domain.org

Perform a directory synchronisation and test the SIP address has been updated correctly


  1. does this still work?

    I just moved from Hybrid to completely online… most of our users are created in our parent domain. & use their UPN to sign into SFB / Email/ 365. However we have some users in our child domain, that we would set their sips to be USer@parentdomain.com , then migrate them up. I updated the primary SIP & added it in PRoxy.

    when i look at the user via lync online powershell it shows the OnPremSipAddress as the address that i set, the proxy address also shows it, but the SIPaddress for the object still shows the users UPN./ this was after a few hours after a sync…

  2. Recently I can no longer just search for a user to assign a Skype number to and must add a SIP under their AD attributes in order for them to show up in the O365 Skype dashboard to assign them a number. Has something recently changed to require this that anyone is aware of? I never had to do it before but have had to do this in the last 3 weeks for 2 new users. We are in a hybrid environment and everything else syncs fine , just the user can’t be found when trying to assign a skype number.

    • Hi
      In hybrid the supported process is to enable on-prem and then move to online. Are you trying to enable online first?

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