Azure Files - System error 53
There are two possible reasons for getting this error if you are trying to mount your Azure file shares from outside of Azure Datacenter via SMB 3.0.
Your client OS needs support SMB 3.0, for example use Windows 8, Windows 10, Windows Server 2012.
The port 445 (TCP Outbound) needs to be opened by your ISP or firewall. The SMB protocol is dependent on this port if you mount from outside of Azure Datacenter, and I do notice some ISP blocked this port (e.g. Comcast).
You can refer to the links below to do a self-check on the port by yourself.
http://poshcode.org/2514
http://powershell.com/cs/media/p/4063.aspx