Sometimes when you delete a SQL Azure server you are not able to recreate it in the portal with the error that the server name already exists. This happens because the server name is cached in the portal system. Officially though, the information is removed very quickly from the SQL Azure backend.
To work around this issue use the resource manager PowerShell cmdlet to create a SQL Azure server with a custom name.
With 1.0+ use: https://msdn.microsoft.com/en-us/library/azure/mt603715.aspx