This was initially a bit of a mystery until I checked the IP of the azure SQL server. 

Googling for “**azure sql cannot create PoolableConnectionFactory**” I came across 
“[Failed to Create PoolableConnectionFactory When Connecting to Azure SQL Server Database from Spring / Hibernate Tomcat Application][1]” on MSDN 
with a recommendation to use **user=username@servername** in the connection string.

So I checked on Azure for the recommended JDBC connection string
[![enter image description here][2]][2]

**Resolution**

Edit C:\SDL\Web\deployer-combined\config\deployer-conf.xml

    <State>
        <Storage Adapter="mssql" driver="com.microsoft.sqlserver.jdbc.SQLServerDriver">
            <Property Name="host" Value="azurename.database.windows.net"/>
            <Property Name="port" Value="1433"/>
            <Property Name="database" Value="Tridion_Broker"/>
            <Property Name="user" Value="TridionBrokerUser@azurename"/>
            <Property Name="password" Value="********"/>
        </Storage>
    </State>

Edit C:\SDL\Web\deployer-combined\config\cd_storage_conf.xml

    <Storage Class="com.tridion.storage.persistence.JPADAOFactory" Id="defaultdb" Type="persistence" dialect="MSSQL">
        <Pool CheckoutTimeout="120" IdleTimeout="120" MonitorInterval="60" Size="10" Type="jdbc"/>
        <DataSource Class="com.microsoft.sqlserver.jdbc.SQLServerDataSource">
            <Property Name="serverName" Value="azurename.database.windows.net"/>
            <Property Name="portNumber" Value="1433"/>
            <Property Name="databaseName" Value="Tridion_Broker"/>
            <Property Name="user" Value="TridionBrokerUser@azurename"/>
            <Property Name="password" Value="*********"/>
        </DataSource>
    </Storage>

I hope this helps you move your solution to Azure SQL.

  [1]: https://social.msdn.microsoft.com/Forums/sqlserver/en-US/42d86f8a-f9f0-44a9-87e2-7005f18ec014/failed-to-create-poolableconnectionfactory-when-connecting-to-azure-sql-server-database-from-spring?forum=ssdsgetstarted&prof=required
  [2]: https://i.sstatic.net/SC1rU.png