The issue has been replicated and confirmed by Office365 engineer team – there is at the moment no solid workaround – but issue is being looked in to.
The problem occurs when you dial out to PSTN from the Skype for Business mobile client on Android/ iOS / WinPhone. The FROM header that is sent in the invite from the Mediation server component in the CCE to the PSTN Gateway is missing the LineUri in the FROM field – and also the ;user=phone is also missing – instead the users sip-address is sent.
Meaning that From header for my test user is
Where it should be
So what does this mean ? – Well 2 things.
When sending this info to a SIP Trunk provider or ISDN – they cannot forward the user name as a valid E.164 number, and also on many platforms calls will be rejected because the FQDN is not contained in the FROM field – so unless the provider has knowledge of the Vanity domain call will fail – because the property ;user=phone is missing
The latter, can be fixed easily by the provider -so they will accept the call – bu the primary issue is that calls originating in the mobile client will show up a callee as “Private number” or unknown.
Only workaround would be 1:1 regex replacement in the gateway – and unless the customer has only a few employees, this is not a feasible solution in my opinion.
By the way – a small “note from the field” always include Wireshark and enable Telnet in the BaseVM before running install-ccinstance 🙂 Saves a few minutes when troubleshooting issues like this.
As always Happy (cloud) SKYPE’ing.