Skype Academy presents Cloud PBX Voicemail with Exchange Server on-premises Summary

I’ve seen this video available for some time on Skype academy and i finally got round to watching it so here’s a summary of the session and some added information. I hope this useful.

Great to see Cloud PBX users can leverage an on premises Exchange deployment for Cloud PBX Voicemail.

Watching the video there are a number of prerequisites and requirements for enabling this and there could be an element of confusion around the use of Azure Voicemail and Exchange UM. Azure VM is still used for voicemail with Exchange server on premises. Also key to note there are some feature missing when using Azure VM Sad smile and also check supportability of existing Exchange Server deployment first and check endpoints compatability.

Link to video –


Speaker Lynnn Roe

Agenda of the session

Previously voicemail options for Cloud PBX relied on having your mailbox in Office 365 (Exchange Online). Voicemail uses Azure Voicemail not Exchange UM and this still seems to be the case if you have Exchange server on premises.

But now Azure Voicemail can leverage your on premises Exchange mailbox with Cloud PBX users. This is great to see this as it allows more flexibility. So now you have mailbox on premises or in Exchange Online Smile


What’s is voicemail for Cloud PBX


KEY POINT – Voicemail is ALWAYS provided by Azure Voicemail it will NOT be provided by Exchange UM.

However Exchange UM policies are required to enable client side features. Voicemail play in Outlook. voicemail displayed in voice tab in SfB client.

Does require a basic exchange dial plan to be configured. UM Mailbox policy to be defined manually with on premises.

Voicemail policy is automatically assigned when online. Manual process on premises.

Some Exchange UM VM feature are not available when using Azure voicemail

  • Play on phone
  • No subscriber Access – not available for Azure Voicemail. Callers cant call into voicemail, listen to calendar or email via PSTN
  • No personal auto attendant – the ability to configure AA is there but it wont work with Azure VM. No real UM functionality

Requirements on end users – No impact on end users

For admin you have to manual configure voicemail on premises! must remember this.



Requirements for mailboxes homed on premises and theres a few of them here


  • Azure AD Sync
  • Exchange DNS points On premises with EWS and autodiscover – Azure VM can learn mailbox is homed on premise
  • Fully configured Exchange Hybrid in place (Mailboxes not migrated)
  • OAuth is configured between Exchange on premises and Office 365 – Enable Azure VM to gain access to users mailboxes on premises
  • Users NOT licenced for Exchange Online – Azure VM
  • Users IS licenced for SfB Online with Cloud PBX
  • Users enabled for UM Dial plan (ON PREMISES Exchange)

The link below expands on the prereqs


KEY POINT – Also published is a supportability matrix which is key to check first.

Note version of Exchange must be Exchange 2013 CU12 which single AD forest.

There are a number of endpoints as well so check this. Lync 2013 client seems be classed as SfB 2013 MSI.




Azure VM elevates mailbox based on licencing to discover mailbox locations.

  • If it has Exchange Online it accesses online mailbox
  • If it doesn’t have a Exchange Online licence it fails and access on premise exchange via EWS and Autodiscover. DNS must be available and accessible externally.

Provides best experience for end users and callers by utilising caching.

DOES require Exchange UM policies

Having Exchange UM policies may cause confusion! i believe it will. Although UM is not used for voicemail processing UM policies are required to be configured. Ouch.

Experience and config requirements for UM policy is the same for on premise and online, difference with online is auto config, on premise is manual by admin


Bit more details on why it works

  • Callers routed initially to Azure voicemail, playback custom voicemail greeting cached
  • Caller experience for person leaving vm is optimised
  • prevents delays for caller leaving vm
  • After vm recorded Azure VM perform lazy back end ops to ensure the next caller has better experience. Lazy ops outside of user experience so no delays or long pauses.
  • Does require and leverage EWs and Autodiscover externally.
  • SMTP failback process, if EWS fails then SMTP will be sent to users inbox.


With diagram as well. Difficult to read fully but you can see how it works.


Calls come in

Azure VM checks for cached custom recordings

If it find cached information this is played to use, if greeting not found a default greeting will be played.

Azure VM will try and authenticate online first, if found send to Exchange online vm if not found route on premises exchange. EWS and Autodiscover used to locate mailbox location. this process could take up to 30 seconds.

After this the information will be cached for the next caller.

SMTP is fall-back if EWS if unavailable.



KEY POINT – SfB Cloud PBX users homed in Office 365 WILL ALWAYS use AZURE VOICEMAIL

KEY POINT – Azure relies on Exchange UM only for client side features to work and be visible. NO UM engine is leveraged for used.

Exchange Hybrid deployment required for Azure VM to locate on premise mailbox


Hope this helps and you found it useful.



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