Typically the two workloads of Exchange Unified Messaging and Office Communications Server with Enterprise Voice were deployed separately. Most Companies adopted Exchange UM before OCS, or Companies were deploying OCS in a pilot scenario and integrating with their existing PBX messaging system.
As these products become more mature we are seeing complete deployments of both workloads. At a recent deployment in a Boston based law firm users are being enabled for OCS enterprise voice as well as Exchange Unified Messaging and abandoning their legacy avaya phone. All of the laywers at this company have a telephone number and a fax number, a common difficulty is that the OCS Mediation server does not support the fax protocol. Therefore when deploying OCS as the main endpoint for a user, call flow comes through the mediation server, any faxes sent over this trunk would fail because the mediation server cannot handle the T.38 protocol.
I read a blog post from Mino (The UC Guy) linked here. Mino explained this scenario with a solution that included a secondary dial plan being assigned to users. The key part to this solution was also a second trunk from the pbx that is routed directly to the Unified Messaging Server instead of through the Mediation server.
At the customer in question we had already setup a separate trunk to the UM Server so they could provide all users with Exchange UM Functionality but slowly Migrate users to OCS for voice. We were already routing the faxes directly to the UM server by modifying the coverage path of their fax extension to our UM Pilot Identifier. You can see on the log from the DMG2120 below that the call was routing to the Exchange UM server without any issues, however in the exchange logs it could not find a user.
For the same reason that we had two seperate trunks for UM only users and OCS-UM users we had a secondary dial plan for TelExtn.
I am not sure if this is a commonly known thing however you must click the down arrow to add a EUM address rather than an SMTP address:
This is the same thing as executing this commandshell command provided in Jen’s blog post:
Set-Mailbox -id Randy Wintle -SecondaryAddress 61 -SecondaryDialPlan UmDialPlan
Once the second extension was added to the user (separate screenshots from the deployment and my internal testing), the fax would route correctly to the user and appear in the user’s mailbox.
Luckily for us we already had the ground work built without realizing the faxes would not go through.Now the next step is to get rid of the Avaya PBX completely and have all users utilizing the full Microsoft UC Platform J