There is a cool feature of Exchange 2007 Unified Messaging that allows you to click on a voicemail message in your outlook inbox and have it played to your cell phone /desk phone /home phone. This comes in handy if you want to listen to the message but you don’t want to play it over your PC speakers (or if you don’t have PC speakers).

If you click the "play on phone" button, you will normally get prompted for the phone number to dial:

Well, here is the bad part. There are two big stumbling blocks. I’ll talk about both:

PROBLEM 1: If you use RPC over HTTPS, this feature doesn’t work. UPDATE – RPC over HTTPS will work if you set the autodiscoer URL properly (see below)

And the worst part is the error message:

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The Microsoft Exchange Unified Messaging service cannot be contacted to play messages on your phone. Try again later.

Thanks, MS, but actually no matter how much later you wait, or how many times you try again, you will not get it to work.

The other bad part is that the voicemail tab in your Outlook options is grayed out. It is very confusing. My suggestion if you are having this issue is to temporarily disable RPC over HTTPS and see if it works.

PROBLEM 2: Failing to Set the UM autodiscover URL properly will cause the same symptoms

What is even more confusing is that there is another problem that causes these exact same behavior: you must have the internal and/or external URL set for the autodiscover service in Exchange 2007. UM uses the autodiscover service to publish the URL of the UM service, which, oddly enough is located on the CAS server. (not so odd, if you think about it for a while – this is how clients access UM, through the "Client Access" server) The default is going to be the internal servername’s FQDN: e.g. "cas-server.domain.local". The trouble is that most people don’t use that name externally, and typically you only have a certificate for the CAS server with the external-facing server name: e.g. mail.domain.com to access OWA etc.

So what you need to do is to set the UM Virtual directory’s internal and external URLs to be the externally available name.

http://technet.microsoft.com/en-us/library/bb124335.aspx

Do not use this URL – the information in it is wrong. There is a "typo" on this page as well as in the set-UMVirtualDirectory commandlet. If you follow the instructions on the help file or technet article, it breaks everything.

The article and helpfile tell you to enter "webservices.aspx" as the page in the UM URL. This will not work. You need to enter the URL as I have posted below, with "service.asmx"

In short, you should get to the Exchange Management Shell and type (on one line):

Set-UMVirtualDirectory -Identity "CAS-Server1UnifiedMessaging (Default Web Site)" -ExternalUrl https://mail.domain.com/UnifiedMessaging/service.asmx -InternalUrl https://mail.domain.com/UnifiedMessaging/service.asmx

Substituting "CAS-Server1" and "mail.domain.com" as appropriate.